* part 2 of the initial doc fixes
- spelling fixes
- grammar fixes
- em-dashes should be em-dashes (`—`): double dashes (`--`) are not rendered properly
- reduce overusage of em-dashes, some of those should be separate sentences
- use the correct syntax for notes, tips and warnings
- every sentence is in a separate line (helps with future diffs)
- add missing dots at the end of list items
- fix some lists
* sentences on separate lines in the remaining files
* 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.