* bump docker compose to use latest supported db and postgis
* update justfile to allow simple legacy testing
* update readme
Followup: implement CI testing -- see #502
This PR re-uses some ideas by @gbip from #448
* move all CI github workflow tests into the dedicated shell scripts
* consolitade two database initialization scripts into one
Note that I manually published [maplibre/martin:latest](https://hub.docker.com/r/maplibre/martin) to docker, so it might be able to pass CI ok. I have not looked deeply into the existing CI workflow - @stepankuzmin any suggestions on changes to that? The github actions are now setup
P.S. I am not certain what that whole `brew/tap` thing is - don't know enough about Macs
