Customize/Add Built-in Shortcuts (including keypresses, like {tab} and {enter})

It seems like there was perhaps once some consideration (https://github.com/Flow-Launcher/Flow.Launcher/pull/930) for additional enhancements to Built-in Shortcuts, and I would like to propose adding the ability to add various hotkey presses to the list, either by default, or just with the ability to customize it by the user. You could re-use the code that captures hotkey sequences for Custom Query Hotkeys, though there would need to be new code for simulating those hotkey sequences in Windows.

I imagine there are all sorts of interesting things that could be done with this addition, but a simple immediate example is that adding the `{enter}` key to the Built-in Shortcuts (or enabling the user to add it) would then provide a solution to https://github.com/Flow-Launcher/Flow.Launcher/issues/2213 for Custom Query Hotkeys being able to automatically trigger when called.

Thanks for considering this idea/request! :)