Docs quality checks

[t0yv0]

We have an opportunity to improve visibility into documentation pipeline by introducing data quality checks. These checks should:

• produce differential reports on data quality on PRs comments, similar to how schema-tools do it
• feed data to S3 that is tagged with Git references so historical analysis can be done with SQL tooling

The easiest path forward is perhaps to build on existing infrastructure that emits quality reports for the examples pipeline, see for example this ticket talks about flushing this data to S3 more fully for a Metabase integration:

• https://github.com/pulumi/ci-mgmt/issues/831

The PR integrations could work by storing a branch-latest version of the report in GitHub actions cache and comparing against.

[t0yv0]

@iwahbe @AaronFriel links to related work/plans here? appreciate it.