feat: Save window position on Linux. Refactor events

* Save Fether window position on Linux using debounce with 'move' event, and 'close' event

* Save Fether window position on macOS and Windows also using 'close' event instead of just 'moved' event

* Refactor `create` method to prevent duplication

* Refactor to organise event listeners into `setupWindowListeners` and `setupRequestListeners`