``Development``: Dark mode in Apollon Standalone

[minrows]

Motivation and Context

This PR implements the Darkmode feature in Apollon Standalone

Description

The feature is as identical to the one we have in Artemis, where users can now have a button to switch between dark mode and light mode.

Steps for Testing

To test locally:

1. checkout the enhancement/dark-mode branch
2. yarn install && yarn start

To test in test server:

1. Goto https://test1.apollon.ase.in.tum.de

Todos:

• [x] Implement toggle switch instead of radio button
• [x] Fix Codacy Static Code Analysis Issue
• [x] Fix styling of File Menu Entries

[bassner]

Looks good in general!

I think there are a few issues left:

Dark Mode popup closes even though it's hovered

The popup auto closes even if I hover it. If I'm not quick enough, I could be unable to click the switch

https://user-images.githubusercontent.com/23171488/168484747-7a5b1e78-4ee7-4f77-aef0-7113a7da343b.mov

Background intensive

The grid background is very intensive in my opinion, especially compared to light mode. It's also less intensive in Artemis. But that's just an opinion

Apollon Standalone:

Artemis:

Separator appears black

The separator in the right sidebar seems to be black in dark mode and is barely visible:

Alert is not themed

This Firefox alert seems to be not themed

[minrows]

• [x] Background intensive
• [x] Separator appears black (Should and will be fixed in the Apollon)
• [x] Alert is not themed
• [x] Dark Mode popup closes even though it's hovered