Docker related updates

[rmfranken]

Hi Holger,

As we use the SHACL api a lot, and have quite some MacOS users, we have updated the docker container to extend support a bit and made it overall more lightweight & robust. Credits for this work go to SDSC collaborators @supermaxiste and @cmdoret .

Major changes:

• Support for ARM architecture (newer MacOS + some Linux distributions)
• Optimized container size (from ~144Mb to ~85Mb)
• Added a git attributes file to prevent windows users accidentally corrupting files using CRLF line-endings instead of LF line endings

Minor changes:

• Updated docker README section to follow major changes

Any feedback is appreciated.

[HolgerKnublauch]

Thanks, I trust you on this one, as usual :)