Migrate to the Userscripts API

This is a very sad commit as we will no longer be supporting Firefox as they do not support the userscripts API. Support for Firefox in upcoming versions will no longer exist, and all related logic has been removed.

Author: MrBlankCoding

README.md

@@ -9,17 +9,6 @@ CodeTweak is a Manifest V3 userscript manager with a built-in editor.
 - Support common GM APIs (`GM_getValue`, `GM_setValue`, `GM_xmlhttpRequest`, etc).
 - Import scripts from Greasy Fork.
 
-## Build (Firefox)
-
-```bash
-npm ci
-npm run build:firefox
-```
-
-- Build script: `buildScripts/build-firefox.js`
-- Output folder: `build/firefox`
-- Firefox package: `build/codetweak-firefox.zip`
-
 ## Build (Chrome)
 
 ```bash
@@ -37,7 +26,6 @@ Output: `build/chrome`
 npm install
 npm run lint
 npm run build:chrome
-npm run build:firefox
 ```
 
 Docs: