Add powershell script to download latest release

## What this change does:
Adds a power-shell script to get the latest release from GitHub and download it if the user does not have it on their disk.

## How to get this working:
Create the following directory structure:
```
---- ventoy
    ---- ventoy-update-windows.ps1
    ---- ventoy-1.0.19-windows.zip
    ---- ventoy-1.0.18-windows.zip
```
When running the script from that directory, it will check the latest downloaded release on disk and compare it with the latest release on GitHub. If a newer version exists, it will download that version in the same directory.

## Future scope of this change:
- Could be added to automate updates within app.
- This approach also allows to get the change-log using `$release.body`.

ventoy-update-windows.ps1

@@ -0,0 +1,28 @@
+# Get the releases from GitHub
+$releases = Invoke-RestMethod -Uri "https://api.github.com/repos/ventoy/Ventoy/releases"
+
+# Iterate through the releases
+forEach ($release in $releases) {
+    # Exclude pre-releases
+    if (!$release.prerelease) {
+        # Get the version of the release
+        $version = $release.tag_name
+        # Iterate through the release assets
+        forEach ($asset in $release.assets) {
+            # Include only Windows assets
+            if ($asset.name -like "*-windows.zip") {
+                # Download only if file does not exist on disk
+                if (Test-Path $asset.name) {
+                    Write-Host "You already have the latest version of Ventoy."
+                    break
+                }
+                else {
+                    Invoke-WebRequest -UseBasicParsing -Uri $asset.browser_download_url -OutFile $asset.name
+                    Write-Host "Downloaded Ventoy for Windows $version."
+                    break
+                }
+            }
+        }
+        break
+    }
+}