Embedding Prosody using AppImage:

Thanks to this commit, there is no more need to manually install Prosody
on the server.
The plugin now build and embed an AppImage of Prosody.

In this commit:
* building and using a Prosody AppImage.
* Adding a launcher in the AppImage: the first command argument tells if
  we want to run prosody or prosodyctl
* prosodyCtl functions now uses the AppImage.
* Prosody AppImage: extract once at the startup, then run the squashfs

server/lib/diagnostic/prosody.ts

@@ -33,6 +33,8 @@ export async function diagProsody (test: string, options: RegisterServerOptions)
 
     result.messages.push(`Prosody will use ${wantedConfig.baseApiUrl} as base uri from api calls`)
 
+    result.messages.push(`Prosody path will be '${wantedConfig.paths.exec}'`)
+
     result.messages.push(`Prosody modules path will be '${wantedConfig.paths.modules}'`)
 
     result.messages.push(`Prosody rooms will be grouped by '${wantedConfig.roomType}'.`)