Add script for generating, commiting and pushing openapi json files

[pedro-psb]

About this PR:

• Depends on: Implement api.json generation in pulp-docs #59
• This want to merge to the docs-data branch, which should only hold the openapi {plugin}-api.json files
• Adds a script that generates the json api files and commit/push them to docs-data branch.
• Add a CI workflow that uses this script and can be triggered manually or via cron

[pedro-psb]

@mdellweg I did the orphan branch trick