Add Radarr Cloudron app packaging

- Add CloudronManifest.json with app configuration
- Add Dockerfile for building Radarr image
- Add start.sh script to launch Radarr
- Add icon.png for app icon
- Update README.md with installation and usage instructions

CloudronManifest.json

@@ -0,0 +1,19 @@
+{
+    "id": "com.radarr.app",
+    "title": "Radarr",
+    "author": "Radarr",
+    "description": "Radarr is a movie collection manager for Usenet and BitTorrent users",
+    "tagline": "Movie organizer/manager for usenet and torrent users",
+    "version": "1.0.0",
+    "healthCheckPath": "/",
+    "httpPort": 7878,
+    "addons": {
+      "localstorage": {}
+    },
+    "manifestVersion": 2,
+    "website": "https://radarr.video/",
+    "contactEmail": "support@radarr.video",
+    "icon": "file://icon.png",
+    "tags": [ "media", "movies", "torrent", "usenet" ],
+    "mediaLinks": [ "https://raw.githubusercontent.com/Radarr/Radarr/develop/Logo/256.png" ]
+  }