- split the installation page into separate pages for Docker, binary install, and packages
- clarify the next step is the installation page via the web
- clarify the first user created has admin rights
- clarify how values in the config sheet are provided when using Docker installation
- explain database preparation can be skipped if using SQLite which is built-in
Fixes: https://codeberg.org/forgejo/docs/issues/117
(cherry picked from commit 64ba97d470)