* 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.
* systemd: use same service file as package
* systemd: recommend setting up a user
* clean up obsolete / ephemeral notes
* eth1 -> execution, in many places
* clean up docker instructions to match the experience of running the
runner script
* add basic instructions / links for execution clients other than geth
* clear a few more references to JSON-RPC, update to REST
* update hardware requirements with execution client extras
* start talking about merge requirements (this needs a dedicated page)
* note that binaries do exist, where relevant
* list gitcoin under donations
* update syncing docs
* `NOT` is for `NOTICE` in logs
* update rpi hardware recommendations
* prevent automatic doppelganger restarts in systemd service file