Updating to manifest v3 format

- Bumped extension version to 3.0.0 since it will be breaking
- Set minimum chrome version to version after introduction of v3
- Background script now needs to be a service worker
- The directive for options_ui changed
- Moved the FireFox specific settings per Mozilla documentation, but still commented out since Chrome doesn't accept it (Originally proposed by @liskin in PR #32)

manifest.json

@@ -1,9 +1,9 @@
 {
   "name": "Add URL To Window Title",
   "author": "Eric H Goldman",
-  "version": "2.2.1",
-  "minimum_chrome_version": "42",
-  "manifest_version": 2,
+  "version": "3.0.0",
+  "minimum_chrome_version": "90",
+  "manifest_version": 3,
   "description": "__MSG_manifestDescription__",
   "homepage_url": "https://github.com/erichgoldman/add-url-to-window-title",
   "icons": {
@@ -20,23 +20,20 @@
     }
   ],
   "background": {
-    "scripts": [ "background.js"]
+    "service_worker": "background.js",
+    "type": "module"
   },
   "options_ui": {
     "page": "options.html",
-    "chrome_style": true
+    "open_in_tab": false
   },
   "permissions": [
-    "activeTab",
     "storage"
-  ]/* "applications" key is required by Firefox, but not accepted by Chrome,
-    * remove this comment when releasing for Firefox  
-  ,
-  "applications": {
+  ]/*,
+  "browser_specific_settings": {
     "gecko": {
       "id": "[email protected]",
       "strict_min_version": "60.0"
     }
-  }
-  */
+  }*/
 }