Restructure documentation

Restructure the documentation into the top-level:

- getting started:
- Installation: basics, extras, links to tutorials, links to method explanation

- tutorials:
- detecting corrupted labels: synthetic influence, CNN (malaria example?)
- outlier analysis: wine
- assigning value to data provider:
- data pruning:
- data selection:

- how-to guides:
- scaling computation
- how to speed up computation with parallelization
- how to speed up computation with caching
- basic setup of valuation objects
- basic setup of influence objects
- choosing and configure samplers
- choosing sample sizes and stopping criteria
- advanced configuration of influence computation
- how to ensure reproducibility

- methods:
- valuation
- influences

- api:
- user api
- development

Take inspiration from
- https://nick.groenen.me/posts/the-4-types-of-technical-documentation/
- https://diataxis.fr/
- https://estimagic.org/en/latest/index.html

Convention:

- do not add math formulas to docstrings, but reference the documentation, explain the implication of parameter choices in docstring
- keep the docstrings as lean as possible and reference the documentation whenever possible
- tutorials should be motivated by tasks

Wish list:
- short summary to check if user is on the correct documentation page
- list of related topics at the beginning of every documentation page