* TLS documentation updates
Move "Bring your own certificates" to the top
since the letsencrypt section is now much longer, it seems wrong to
keep such a short section way down at the bottom.
Restructure "Challenge types" into separate sections
Add technical description of letsencrypt renewals
this aims to answer:
- what can be expected in terms of renewals
- what logs can be expected (none)
- how to validate that renewal happened successfully
- the reason for some of the 'acme/autocert' logs, or at least
some best-effort assumptions
* +prettier
