* reorganise navigation menus
* update light client guide with comparison table
* add suggested fee recipient and JWT secrets to the merge guide
* add some background info to book readme
* add JWT docs
also limit toc to make it displayable with substeps.
* update docs
* introduce mdbook-admonish for nice looking callouts
* new section on data directory
* recommend source build for advanced users and direct the rest to
binaries
* more strongly highlight that execution client is needed
* write an actual deposit guide
* remove cruft / fix links / etc
Jacek Sieka
Ștefan Talpalaru
Sacha Saint-Leger