chore: prepare the 1.3.0 release

Version 1.3.0 (manifest "1.3"): the options page rewrite adds features
without breaking changes, and addons.mozilla.org needs a version above
the live 1.2. The lockfile's root version moves with it. Unreleased
becomes the 1.3.0 section.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "search-with-chatgpt-powered-by-openai-extension",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "search-with-chatgpt-powered-by-openai-extension",
-      "version": "1.2.0",
+      "version": "1.3.0",
       "devDependencies": {
         "web-ext": "10.5.0"
       },