[docs] Brush up the documentation

* Try to organize after expected user need
* Update mkdocs stuff and fix a broken link
* Move web building info to building.md
* Add info about Roku Soundbridge
* Add note about Google Nest not working

docs/audio-outputs/airplay.md

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+# AirPlay devices/speakers
+
+OwnTone will discover the AirPlay devices available on your network. For
+devices that are password-protected, the device's AirPlay name and password
+must be given in the configuration file. See the sample configuration file
+for the syntax.
+
+If your Apple TV requires device verification (always required by Apple TV4 with
+tvOS 10.2) then you can do that through Settings > Remotes & Outputs in the web
+interface: Select the device and then enter the PIN that the Apple TV displays.
+
+If your speaker is silent when you start playback, and there is no obvious error
+message in the log, you can try disabling ipv6 in the config. Some speakers
+announce that they support ipv6, but for some reason don't work with OwnTone.
+
+If the speaker becomes unselected when you start playback, and you in the log
+see "ANNOUNCE request failed in session startup: 400 Bad Request", then try
+the Apple Home app > Allow Speakers & TV Access > Anyone On the Same Network
+(or Everyone).

docs/audio-outputs/chromecast.md

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+# Chromecast
+
+OwnTone will discover Chromecast devices available on your network, and you
+can then select the device as a speaker. There is no configuration required.
+
+Take note that:
+
+- Chromecast playback can't be precisely sync'ed with other outputs e.g. AirPlay
+- Playback to Google Nest doesn't work

docs/audio-outputs/local-audio.md

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+# Local audio
+
+## Local audio through ALSA
+
+In the config file, you can select ALSA for local audio. This is the default.
+
+When using ALSA, the server will try to synchronize playback with AirPlay. You
+can adjust the synchronization in the config file.
+
+For most setups the default values in the config file should work. If they
+don't, there is help [here](../advanced/outputs-alsa.md)
+
+## Local audio, Bluetooth and more through PulseAudio
+
+In the config file, you can select PulseAudio for local audio. In addition to
+local audio, PulseAudio also supports an array of other targets, e.g. Bluetooth
+or DLNA. However, PulseAudio does require some setup, so here is a separate page
+with some help on that: [PulseAudio](../advanced/outputs-pulse.md)
+
+Note that if you select PulseAudio the "card" setting in the config file has
+no effect. Instead all sound cards detected by PulseAudio will be listed as
+speakers by OwnTone.
+
+You can adjust the latency of PulseAudio playback in the config file.

docs/audio-outputs/mobile.md

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+# Listening on your Mobile Device
+
+## iOS
+
+On iOS, the options are limited because there are no Media Client apps with DAAP
+support and because Apple doesn't allow AirPlay receiver apps. OwnTone also
+can't share music via Home Sharing, which is the protocol Apple uses for sharing
+media between devices.
+
+That leaves the following options, which all rely on OwnTone's streaming:
+
+- listen via the [web interface](web.md)
+- use a [MPD client app](../control-clients/mobile.md#mpd-client-apps) that supports local playback
+- connect to the [streaming](streaming.md) endpoint with a media player like VLC
+
+## Android
+
+On Android, you can use the same streaming methods described for iOS, but you
+can also find apps that act as AirPlay receivers.

docs/audio-outputs/roku.md

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+# Roku devices/speakers
+
+OwnTone can stream audio to classic RSP/RCP-based devices like Roku Soundbridge
+M1001 and M2000.
+
+If the source file is in a non-supported format, like flac, OwnTone will
+transcode to wav. Transmitting wav requires some bandwidth and the legacy
+network interfaces of these devices may struggle with that. If so, you can
+change the transcoding format for the speaker to alac via the [JSON API](../json-api.md#change-an-output).

docs/audio-outputs/streaming.md

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+# Streaming
+
+The streaming option is useful when you want to listen to audio played by
+OwnTone in a browser or a media player of your choice [^1],[^2].
+
+You can control playback via the web interface or any of the supported control
+clients.
+
+## Listening to Audio in a Media Player
+
+To listen to audio being played by OwnTone in a media player, follow these
+steps:
+
+1. Start playing audio in OwnTone.
+2. In the web interface, activate the stream in the output menu by clicking
+   on the icon :material-broadcast: next to HTTP Stream.
+   After a few seconds, the audio should play in the background.
+3. Copy the URL behind the :material-open-in-new: icon next to HTTP Stream.
+4. Open the copied URL with the media player, e.g., VLC.
+   The URL is usually
+   [http://owntone.local:3689/stream.mp3](http://owntone.local:3689/stream.mp3)
+   or http://SERVER_ADDRESS:3689/stream.mp3
+
+## Notes
+
+[^1]: On iOS devices, the streaming option is the only way of listening to your
+      audio, since Apple does not allow AirPlay receiver apps, and because
+      Home Sharing cannot be supported by OwnTone.
+
+[^2]: For the streaming option to work, MP3 encoding must be supported by
+      `libavcodec`. If it is not, a message will appear in the log file.
+      For example, on Debian or Ubuntu, MP3 encoding support is provided by the
+      package `libavcodec-extra`.

docs/audio-outputs/web.md

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+# Listening to Audio in a Browser
+
+To listen to audio being played by OwnTone in a browser, follow these
+steps:
+
+1. Start playing audio in OwnTone.
+2. In the web interface, activate the stream in the output menu by clicking
+   on the icon :material-broadcast: next to HTTP Stream.
+   After a few seconds, the audio should play in the background [^1].
+
+![Outputs](../assets/images/screenshot-outputs.png){: class="zoom" }
+
+For the streaming option to work, MP3 encoding must be supported by
+`libavcodec`. If it is not, a message will appear in the log file. For example,
+on Debian or Ubuntu, MP3 encoding support is provided by the package
+`libavcodec-extra`.
+
+[^1]: On iOS devices, playing audio in the background when the device is locked
+      is not supported in a private browser tab.