fix: bring the draggable area back on MacOS

[cino]

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Description of Change

This change brings the "invisible" draggable area back on macOS, the reason this was removed was that the elements behind it weren't clickable anymore. However, the reason this was happening wasn't actually because of the draggable area but because of the feature that enables the window to be maximized by double-clicking that area (hence the capturing of click events).

My proposed solution is to bring the draggable area back and reduce the double-click area to 10px which increases the area where you can click and expect the normal behaviour.

Motivation and Context

• To improve UX and allow the window to be dragged while on macOS without visible draggable area

This should fix:

• Bug: can't move window in mac #370
• Bug: Toolbar not clickable in the horizontal area that OS level UI components plus padding use #347
• While still keeping Fix navigation toolbar buttons not being clickable (fixes #347) #348 happy as well

Checklist

• My pull request is properly named
• The changes respect the code style of the project (npm run prepare-code)
• npm test passes
• I tested/previewed my changes locally

[j7e]

Per the reply to #793 - #793 (comment) - after exploring further, the Settings screen referred to in the reply is not directly accessible from the splash screen menu bar but only available once the user is past the splash screen, either by logging in or using without an account. The fix is not obvious to a new user; because Ferdium didn't behave in a standard way, my initial impression was that it was broken. At this point, a new user might reasonably conclude the same and abandon it, which does not seem desirable.

Could I suggest i) something on the splash screen to draw attention to troubleshooting issues (or this issue in particular) and ii) making the Settings screen available from the splash screen menu bar?