letsencrypt: document UI configuration, automation, cert usage (#3299)

* feat: add UI configuration, automation, cert usage

- Add information where to enter configuration at all
- Rewrite configuration guide to be UI first
- Add guide on how to renew certificates
- Add details and example on how to use the certificates in the Home
  Assistance default installation
- Resort DNS provider data: now all in one place and not spread, also
  long lists hidden behind details

* fix: add summary to DNS details

* feat: simplify automation creation steps, update dns list

* fix typos

* fix typo introduced when fixing typos

* wrap long lines in new paragraphs

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Co-authored-by: Jan Čermák <sairon@users.noreply.github.com>