Electron: Windows opened from a sandboxed top-level document do not inherit its sandbox restrictions

Impact Windows opened from a sandboxed top-level document did not inherit that document's HTML sandbox restrictions, so content that was meant to run sandboxed could open a window with the app's full origin. GHSA-hq2x-r82h-9wj4 covers the same issue for sandboxed iframes. Apps are only affected i...