Fix #180: Letsencrypt import not working

Letsencrypt certificate import procedure was not working on server that had never installed Prosody.
Adding `prosody_user` in the Prosody configuration file to fix this.
Updating the procedure: the `chown` is no more needed in `/etc/letsencrypt/renewal-hooks/deploy/prosody.sh`.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "peertube-plugin-livechat",
   "description": "PeerTube plugin livechat: offers a way to embed a chat system into Peertube.",
-  "version": "7.0.1",
+  "version": "7.0.2",
   "license": "AGPL-3.0",
   "author": {
     "name": "John Livingston",