Add support for self-hosted updates

package.json

 {
-  "description": "Local emulation of Content Delivery Networks.",
   "author": "Thomas Rientjes",
+  "description": "Local emulation of Content Delivery Networks.",
+  "hasEmbeddedWebExtension": true,
+  "homepage": "https://decentraleyes.org",
+  "id": "legacy@decentraleyes.org",
   "license": "MPL-2.0",
-  "title": "Decentraleyes",
-  "version": "1.4.2",
   "main": "lib/main.js",
-  "homepage": "https://addons.mozilla.org/firefox/addon/decentraleyes",
   "name": "decentraleyes",
-  "id": "jid1-BoFifL9Vbdl2zQ@jetpack",
-  "hasEmbeddedWebExtension": true,
+  "preferences-branch": "jid1-BoFifL9Vbdl2zQ@jetpack",
+  "title": "Decentraleyes",
+  "updateURL": "https://decentraleyes.org/legacy/update.rdf",
+  "version": "1.4.2",
+
+  "engines": {
+    "firefox": ">=38.0a1 <=56.*",
+    "fennec": ">=38.0a1 <=56.*",
+    "seamonkey": ">=2.0a1 <=2.49"
+  },
+
   "permissions": {
     "multiprocess": true
-  },
-  "engines": {
-    "firefox": ">=38.0a1",
-    "fennec": ">=38.0a1",
-    "seamonkey": ">=2.0a1 <=2.46",
-    "{8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4}": ">=27.1.0b1 <=28.*"
   }
 }