Add cache clearing documentation for electron-updater

- Introduced CLEAR-UPDATE-CACHE.md to guide users on clearing the electron-updater cache across macOS, Windows, and Linux.
- Added programmatic method for cache clearing in JavaScript.
- Enhanced update handling in main.js and preload.js to support new update events.
- Updated GUI styles for download buttons and progress indicators in update.js and style.css.

main.js

@@ -731,6 +731,7 @@ ipcMain.handle('check-for-updates', async () => {
       return {
         updateAvailable: result?.updateInfo ? true : false,
         version: result?.updateInfo?.version,
+        newVersion: result?.updateInfo?.version,
         currentVersion: app.getVersion()
       };
     }