Improove accessability of Harbor

[MaxRink]

Currently Harbor doesn't score well when it comes to accessability.
The most used Guidlines are the WCAG (https://www.w3.org/TR/WCAG20/), sadky Harbor currently only follows some parts of the Advice outlined there.

[xaleeks]

It's something we plan on putting some time into, any specific criticism or insight would be appreciated as well

[MaxRink]

We got two imediate things as feedback:
Contrast: both current schemes dont offer high contrast for visually impared users
Ability to navigate just using the keyboard: There a quite few sections of the UI that you cant use just with an keyboard (the sidebar on the left for example) which makes it hard to impossible for users with screenreaders to navigate

[github-actions]

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