fix(bug): updated manifest,json for Firefox (#1399)

* added gecko to ff manifest

* updated min_version

packages/extension/manifest_firefox.json

@@ -14,6 +14,12 @@
     "default_title": "polkadot{.js}",
     "default_popup": "index.html"
   },
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "polkadotjavascript@gmail.com",
+      "strict_min_version": "108.0.2"
+    }
+  },
   "content_scripts": [{
     "js": ["content.js"],
     "matches": ["http://*/*", "https://*/*"],
@@ -39,4 +45,4 @@
   "content_security_policy": {
     "extension_pages": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'"
   }
-}
+}