Make favicon paths configurable

The favicons were hardcoded in launch.html, so
rebranding the page required editing the template.

The paths now come from the favicons block in
assets/config.json. Missing keys keep the defaults
from launch.html.

README.md

@@ -18,6 +18,7 @@ Rename `assets/config.json.sample` to `assets/config.json`.
 | `launchTimeout` | Timeout in ms before the browser fallback is shown after trying to start the jitsi-meet-electron client. |
 | `backgroundImage` | Path to the page background image. Empty: no background. |
 | `logo` | Path to the logo shown in the logo bar. Empty: logo bar stays hidden. |
+| `favicons` | Paths to the page icons: `ico` (fallback icon), `svg` (icon), `appleTouch` (Apple touch icon). The values from `launch.html` are kept if a key is missing. |
 | `downloads` | Download URLs for the jitsi-meet clients, shown in the fallback view per detected OS: `windows`, `macos`, `linux`, `ios`, `android`. |
 
 ## Third-party assets