Fix afterSign.js to properly skip on non-macOS platforms

- Check electronPlatformName instead of process.platform for cross-platform builds
- Prevents error when building Windows on macOS
- Version bump to 2.20.0

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: steveseguin

afterSign.js

@@ -3,11 +3,13 @@ const path = require('path');
 var electron_notarize = require('electron-notarize');
 
 module.exports = async function (params) {
+    console.log('afterSign hook triggered', params);
+    
     // Only notarize the app on Mac OS only.
-    if (process.platform !== 'darwin') {
+    if (params.electronPlatformName !== 'darwin') {
+        console.log('Skipping notarization - not macOS');
         return;
     }
-    console.log('afterSign hook triggered', params);
 
     // Same appId in electron-builder.
     let appId = 'ninja.vdo'