Migrate docs to Zensical

[misode]

Re-adds the docs using Zensical

Differences

• Different UI, navigation and search, but an improvement imo
• The Jupyter notebook outputs from the "General overview" page were not possible to keep
• Added instructions to setup virtual environment, similar to Zensical's instructions

Tasks

• Do we want to "cleanup" the zensical.toml file by removing the comments?
• All I've done is made the accent color red. Do we want any other theme/style changes?
• Can we test the docs build in CI on pull requests?

Screenshots