Redesign Website Mainpage

[zieglerSe]

Currently uses Fornax, which is nice but not best fit for the usecase.

We will redesign it with Feliz.React finishing some of the issues on the respective repository during refactoring.

• import bulma via sass instead of the header css reference fslaborg.github.io#11
• Reduce visual noise, implement light/dark theme fslaborg.github.io#48
• Add sponsors/testimonials section fslaborg.github.io#49
• Fetch github project information and display on mainpage fslaborg.github.io#51
• Fetch github discussion information and display on mainpage fslaborg.github.io#52

This will also deprecate all issues related to former framework specific tools.

@Freymaurer