* initial DOCS.md for Addon
* links to Mosquitto and Adguard
* replaced _ by . for PV-Strings
* mentioned add-on installation method in README.md
* fix most of the markdown linter warnings
* add missing alt texts
* added nice add repository to my Home Assistant badges
---------
Co-authored-by: Michael Metz <michael.metz@siemens.com>
Co-authored-by: Stefan Allius <stefan.allius@t-online.de>
