Release 0.6.1: fix Electron main entry

- add missing main lib/backend/electron-main.js to apps/electron
- yarn build:electron clean, yarn start:electron reaches ready

apps/electron/package.json

@@ -2,6 +2,7 @@
   "private": true,
   "name": "modula2-ide-electron",
   "version": "0.1.0",
+  "main": "lib/backend/electron-main.js",
   "dependencies": {
     "@theia/core": "1.75.0",
     "@theia/editor": "1.75.0",

package.json

@@ -1,7 +1,7 @@
 {
   "private": true,
   "name": "modula2-ide",
-  "version": "0.6.0",
+  "version": "0.6.1",
   "description": "GNU Modula-2 IDE built on Eclipse Theia",
   "engines": {
     "node": ">=24",