chore(docs): restructure and rewrite content in documentation and quality standards chapters

[BirgitBader]

Context

• Closes issue 15
• Removes accordions to better display the content hidden behind them.
• Uses TOCs to access the different sub-sections.
• Rewrites and trims documentation chapter.

To reviewers

• Check if the restructuring helps to better digest and access the provided content.
• Check if rewriting leads to optimization of the chapters.
• Fix any typos or grammar you might find.
• Add anything that you see missing.

[BirgitBader]

@thake It would be great if you could review this :)

[thake]

Thanks for the effort! Just some minor things. @cgebken made a very thorough review!