Show all keybinds mapped to a key in keyboard view

[WeirdRubberDuck]

closes OpenSpace/OpenSpace#3679

Also fixes some styling-related issues when multiple mapped keys were shown.

Here's what it looks like now. New/updated parts highlighted in pink

1. Scrollbar on keyboard instead of entire window
2. Show how many actions mapped to a certain key
3. Scrollbar on just the bottom part, where the list of mapped actions are (note that I could not get it to work for just the actions list, so the title scrolls too...)
4. Show keybind for each action card (necessary now that we show e.g. the SHIFT+X key on selecting X)

[alexanderbock]

How hard would it be to have the keyboard view shrink proportionally instead of having a scrollbar?

[WeirdRubberDuck]

How hard would it be to have the keyboard view shrink proportionally instead of having a scrollbar?

I didn't look into it in great detail, but it seemed "hard" to me since we are currently setting all the sizes to exact pixels in the CSS file. My impression was that it would be time-consuming and hard to update the CSS to get it to work in a way that looks good when resizing, and the scrollbox seemed like a very easy compromise that at least works better than it did before

[alexanderbock]

We'll leave it then 👍