Add missing documentation for configuration options

general/administration/configuration.md

@@ -81,7 +81,8 @@ The main server configuration is built upon the ASP .NET [configuration framewor
 4. **Environment variables**: The [documentation](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1#environment-variables) provided by Microsoft explains how to set these configuration options via environment variables. Jellyfin uses its own custom `JELLYFIN_` prefix for these variables. For example, to set a value for the `HttpListenerHost:DefaultRedirectPath` setting, you would set a value for the `JELLYFIN_HttpListenerHost__DefaultRedirectPath` environment variable.
 5. **Command line options**: Certain command line options are loaded into the configuration system and have the highest priority. The following command line options are mapped to associated configuration options.
 
-    - The `--nowebcontent` command line flag sets the `hostwebclient` configuration setting to false
+    - `--nowebcontent` sets the `hostwebclient` configuration setting to false
+    - `--plugin-manifest-url` sets a value for the `InstallationManager:PluginManifestUrl` configuration setting
 
 ### Main Configuration Options
 
@@ -90,6 +91,8 @@ This section lists all the configuration options available and explains their fu
 |Key|Default Value|Description|
 |---|-------------|-----------|
 |`hostwebclient`|`True`|Set to `True` if the server should host the web client.|
+|`HttpListenerHost:DefaultRedirectPath`|`"web/index.html"` if `hostwebclient` is true; `"swagger/index.html"` if `hostwebclient` is false|The default redirect path to use for requests where the URL base prefix is invalid or missing|
+|`InstallationManager:PluginManifestUrl`|`"https://repo.jellyfin.org/releases/plugin/manifest.json"`|The URL for the plugin repository JSON manifest.|
 |`FFmpeg:probesize`|`"1G"`|Value to set for the FFmpeg `probesize` format option. See the FFmpg [documentation](https://ffmpeg.org/ffmpeg-formats.html#Format-Options) for more details.|
 |`FFmpeg:analyzeduration`|`"200M"`|The value to set for the FFmpeg `analyzeduration` format option. See the FFmpg [documentation](https://ffmpeg.org/ffmpeg-formats.html#Format-Options) for more details.|
 |`playlists:allowDuplicates`|`True`|Whether playlists should allow duplicate items or automatically filter out duplicates.|