switch from yarn to npm

This eases build setup. Where Yarn requires a separate package
repository, npm is available in the standard one.

yarn's package repository signature was recently expired, and apparently
will expire again in a year. Avoid dealing with that.

Fixes #110.

guide/build.md

@@ -111,6 +111,8 @@ To build the server, you will need the following C libraries installed:
 * [`ncursesw`](https://www.gnu.org/software/ncurses/), the UTF-8 version of
   the `ncurses` library.
 
+To build the UI, you'll need [node and npm](https://nodejs.org/en/download/).
+
 On recent Ubuntu or Raspbian Linux, the following command will install
 all non-Rust dependencies:
 
@@ -122,6 +124,7 @@ $ sudo apt-get install \
                libavutil-dev \
                libncurses-dev \
                libsqlite3-dev \
+               npm \
                pkgconf \
                sqlite3 \
                tzdata
@@ -131,15 +134,12 @@ On macOS with [Homebrew](https://brew.sh/) and Xcode installed, try the
 following command:
 
 ```
-$ brew install ffmpeg yarn
+$ brew install ffmpeg node
 ```
 
 Next, you need Rust 1.45+ and Cargo. The easiest way to install them is by
 following the instructions at [rustup.rs](https://www.rustup.rs/).
 
-Finally, building the UI requires [yarn](https://yarnpkg.com/en/). (On macOS,
-the `brew` command above installs it for you. On Linux, follow yarn's guide.)
-
 Once prerequisites are installed, you can build the server and find it in
 `target/release/moonfire-nvr`:
 
@@ -149,12 +149,12 @@ $ cargo test
 $ cargo build --release
 ```
 
-You can build the UI via `yarn` and find it in the `ui/dist` directory:
+You can build the UI via `npm` and find it in the `ui/dist` directory:
 
 ```
 $ cd ui
-$ yarn
-$ yarn build
+$ npm install
+$ npm run build
 ```
 
 ### Running interactively straight from the working copy

guide/developing-ui.md

@@ -21,7 +21,7 @@ this in the webpack documentation.
 Checkout the branch you want to work on and type
 
     $ cd ui
-    $ yarn start
+    $ npm run start
 
 This will pack and prepare a development setup. By default the development
 server that serves up the web page(s) will listen on
@@ -55,7 +55,7 @@ as described
 Thus one could connect to a remote Moonfire NVR by specifying its URL as
 follows:
 
-    $ MOONFIRE_URL=https://nvr.example.com/ yarn start
+    $ MOONFIRE_URL=https://nvr.example.com/ npm run start
 
 This allows you to test a new UI against your stable, production Moonfire NVR
 installation with real data.
@@ -64,7 +64,7 @@ The default `MOONFIRE_DEV_HOST` is suitable for connecting to the proxy server
 from a browser running on the same machine. If you want your server to be
 externally accessible, you may want to bind to `0.0.0.0` instead:
 
-    $ MOONFIRE_DEV_HOST=0.0.0.0 yarn start
+    $ MOONFIRE_DEV_HOST=0.0.0.0 npm run start
 
 Be careful, though: it's insecure to send your production credentials over a
 non-`https` connection, as described more below.