Add high contrast schemes

[LukasKalbertodt]

Draft as there is still more work to be done. @narickmann will probably take it from here.

[narickmann]

The high contrast mode (hc mode) should now be finished.

Here are some more thoughts I have:

1. The boxShadow was removed everywhere for hc mode. A value for this was set for darkmode and lightmode (--shadow-color), but not in hc mode and it is actually ignored.
   I still set it to none for hc mode because I'm not sure whether that could otherwise cause problems at some point and in some places the --shadow-color is not used, but a hardcoded value which would be used in hc mode.
   I think we shouldn't use boxShadow in hc mode because it might be confusing and might not have enough contrast. But I couldn't find anything explicit about it in the WCAG.

2. Let me know what you think about the play-/pause button in the "Review and trim" step when you hover over it.

3. I'm not sure what we should do with the "video-settings" button. I think we should we leave it as it is? (I didn't changed it). If anyone has other thoughts or suggestions, leave a comment.

4. If the hc mode comes into Studio like this, we should adjust the hc mode (for some elements) in the editor. The goal with the new design was to make the applications look related/similar (correct me if I'm wrong). At first glance, this would affect the colors of the drop-down menus (in Studio they have a black/white bg when hovering and in the editor the accent color) and some buttons.

And also let me know if I missed something.

[LukasKalbertodt]

Sorry, I missed the notification for your push+comment!

I like what you've done! I tested it in light hc and dark hc and basically everything looks very high contrast and good (well, for a high contrast mode). The play/pause button you asked about seems fine to me. I only have a few things I noticed while testing:

• The cut buttons could use an outline on hover? Their hover effect is very subtle. Well ok, there is the tooltip, which isn't very subtle... maybe that's enough. You decide.
• In the trimming step: the contrast/difference between the timeline that's already played and that is about to play is fairly low. I think it would be possible to make the "about to be played" part a bit brighter (in light hc) and still have enough contrast to the background.
• The "Discard" button has high contrast, but the red is not really coming through. So these users would miss out on the warning color. Maybe it's worth it making the button background red? Then it would be super heavy of course. Just an idea, no opinion I think 🤷
• In dark hc, the floating boxes for shortcuts and info have the same background than the main part and no border. Thus its not really clear where the box starts and ends. I would probably just add a bright border? Alternatively the overlay should be white-semi-transparent instead of black-semi-transparent.
• In dark hc, the links in the "info" box are not colored. But they could easily be colored like in light hc right?

And a few code comments, but these should all be quick to fix, and most of them are the same "kind of comment" just in multiple places.

[LukasKalbertodt]

Since Nadine will be absent for the coming two weeks, I quickly fixed most of my comments (and rebased). Some of the less opinionated comments I didn't change. It's still fine like this.

Since I only added very little extra stuff and already reviewed otherwise, I will merge.