[Feature] Add Ameba to CI runs

[kosstennbl]

If Ameba would be removed from dependencies and crystal-version would be updated (#2157, #2158), we can re-add Ameba to testsuite, but not in form of shard dependency, but rather as a tool in our CI

Proposal is to add a new workflow to GitHub actions, which would build ameba from sources and then run static lint on a repo.
Together with that, all issues would have to be fixed (1500+ LOC), but most of them are very simple and can be auto-corrected.

Instructions for installation and usage:
https://github.com/crystal-ameba/ameba