fix(appx): App sandbox not enabled (ITMS-90296) (#4244)

The issue in detail is explained here
electron/osx-sign#192

Author: vaibhavtel

packages/app-builder-lib/templates/entitlements.mac.plist

@@ -2,10 +2,12 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
   <dict>
+    <key>com.apple.security.app-sandbox</key>
+    <true/>
     <key>com.apple.security.cs.allow-unsigned-executable-memory</key>
     <true/>
     <!-- https://github.com/electron-userland/electron-builder/issues/3940 -->
     <key>com.apple.security.cs.disable-library-validation</key>
     <true/>
   </dict>
-</plist>
+</plist>