Enable Context Isolation in Electron Fiddle

This project aims to get rid of the Node environment from the renderer process for Electron fiddle to enforce a stronger security model. Basically, with the release of Electron v12.0.0, it is now made default to set the contextIsolation as true which prevents the usage of powerful Node APIs in the renderer process. However, these changes aren’t yet reflected in fiddle’s architecture due to which it currently uses an outdated security model. Therefore, over the summer I plan to refactor Electron fiddle by migrating all the Node APIs used in renderer process to main process and later call them via IPC events.