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

package.json

@@ -88,6 +88,7 @@
     "clean:light": "rm -rf dist/*",
     "prepare": "npm run clean && npm run build",
     "build:converse": "bash conversejs/build-conversejs.sh",
+    "build:prosody": "bash build-prosody.sh",
     "build:images": "mkdir -p dist/client/images && npx svgo -f public/images/ -o dist/client/images/",
     "build:avatars": "mkdir -p dist/server/avatars && ./build-avatars.js",
     "build:webpack": "webpack --mode=production",
@@ -95,7 +96,7 @@
     "build:serverconverse": "mkdir -p dist/server/conversejs && cp conversejs/index.html dist/server/conversejs/",
     "build:prosodymodules": "mkdir -p dist/server/prosody-modules && cp -r prosody-modules/* dist/server/prosody-modules/",
     "build:styles": "sass assets:dist/assets",
-    "build": "npm-run-all -s clean:light -p build:converse build:images build:avatars build:webpack build:server build:serverconverse build:prosodymodules build:styles",
+    "build": "npm-run-all -s clean:light -p build:converse build:prosody build:images build:avatars build:webpack build:server build:serverconverse build:prosodymodules build:styles",
     "lint": "npm-run-all -s lint:script lint:styles",
     "lint:script": "npx eslint --ext .js --ext .ts .",
     "lint:styles": "stylelint 'conversejs/**/*.scss' 'assets/**/*.css'",