Update manifest.json

Fix manifest.json so and allows the extenstion to be self-installed in Firefox

manifest.json

@@ -4,11 +4,11 @@
   "version": "2.0",
   "description": "Eight Dollars can help you tell the difference between actual verified accounts and twitter blue users.",
   "icons": {
-    "16": "./assets/16.png",
-    "32": "./assets/32.png",
-    "48": "./assets/48.png",
-    "256": "./assets/256.png",
-    "512": "./assets/512.png"
+    "16": "/assets/16.png",
+    "32": "/assets/32.png",
+    "48": "/assets/48.png",
+    "256": "/assets/256.png",
+    "512": "/assets/512.png"
   },
   "content_scripts": [
     {
@@ -24,11 +24,16 @@
   ],
   "action": {
     "default_icon": {
-      "16": "./assets/16.png",
-      "32": "./assets/32.png"
+      "16": "/assets/16.png",
+      "32": "/assets/32.png"
     },
     "default_title": "Eight Dollars - Options",
-    "default_popup": "options/options.html"
+    "default_popup": "/options/options.html"
   },
-  "permissions": ["storage"]
+  "permissions": ["storage"],
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "eight-dollars@github.com"
+    }
+  }
 }