Automate generation of compatibility report (in-repo)

[jsumners-nr]

#2157 targets automating updates of the New Relic docs website. That will require collaboration with the docs team and some research. In the meantime, we can solve adding the compatibility doc to our repo.

A successful outcome of this ticket is:

1. the presence of a compatibililty.md doc in the repo
2. the generation of that doc through CI (both automatic on versioned tests updates and through a manual trigger)
3. a link to the compatibility doc in the main README.md

[workato-integration]

https://new-relic.atlassian.net/browse/NR-264477