[FEATURE REQ] New readme.md repo PR check to enforce Azure service versioning

### API Spec link

NA

### API Spec version

NA

### Please describe the feature.

Each Azure service version must consist of operations that all share the same api-version.
Also, a service cannot mix & match stable and preview operations.
This is required for docs, SDK versions, and more.

This feature request is to add a PR check that looks at a new readme.md file, finds the latest default "tag".
This value MUST be of the format YYYY-MM-DD and can have an optional -preview suffix, or the tag value is an error and the PR cannot be merged.

In the readme.md's "input-file:" section, all paths MUST have a version that matches the tag value exactly, or the PR cannot be merged. SIDENOTE: This ensures that a preview version consists of only preview json files and a stable version consists of only stable json files.

It is an error and the PR cannot be merged if a json file exists in the version folder that is missing from the "input-file:" section. This catches a bug where the json file exists but was forgotten to be added to the "input-file:" section.