.github/workflows: add riot-ryot.yml
.github/workflows: add riot-ryot.yml

Add github actions configuration to run all tests on BOARDs
connected to ci-riot-tribe.

Will run on all new Release Candidates and weekly on master.

miri64/RIOT,ant9000/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kaspar030/RIOT,OTAkeys/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OTAkeys/RIOT,kYc0o/RIOT,OlegHahm/RIOT,miri64/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,kYc0o/RIOT,ant9000/RIOT,miri64/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,OTAkeys/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,ant9000/RIOT,miri64/RIOT,OTAkeys/RIOT,miri64/RIOT,ant9000/RIOT,OlegHahm/RIOT,kaspar030/RIOT,kaspar030/RIOT,kYc0o/RIOT,authmillenon/RIOT,OlegHahm/RIOT,jasonatran/RIOT,kaspar030/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,jasonatran/RIOT