Revisit documentation part 1: divio-like landing page, installation page, configuration page (#1233)
* Refactor to divio-like documentation
* add overview pages
* Write installation guide
* small refacto in installation
* 1 work
* add configuration page
* typoes
* Add optional dependencies section
* set back guides folder to avoid dead links for now
* fix links
* fix broken links
* broken url
* remove tutorials and concepts empty parts
* move congifuration guide to environment_varibale reference
* Apply suggestions from code review
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
* missing dot
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>