Dev Tools Menu should open in a dedicated window

[nkolba]

As per issue #43... Currently, if the main window size is too small, the '...' menu for dev tools wraps so that the menu items become obscured. This happens because the toolbar is being rendered in a window that is truncated by the browser view for rendering the tab content. The current menu for devtools is rendered in the DOM of the toolbar window - so if there isn't enough space - it just gets cutoff.

The solution is to use the same method for rendering this menu as is used for the color picker menu, search results, etc, which is to render as a dedicated window that can overlay the content of the main window and is not bound by it's DOM.

[nkolba]

Actually, taking another look, this should be resolvable with the Electron menu apis https://www.electronjs.org/docs/latest/api/menu

[nkolba]

addressed with PR #45