Enforce best practice for package tags in manifests

Description of the new feature/enhancement

Enforce the defined tag best practice in manifest files defined at https://github.com/microsoft/winget-pkgs/blob/master/doc/manifest/schema/1.0.0/defaultLocale.md#tags, to wit, "present these terms in all lower case with hyphens rather than spaces."

Proposed technical implementation details (optional)

This would be a two-part job, and each part can be implemented independently:

• Update the CI validation scripts run over pull requests to reject PRs that use tags with upper-case characters and spaces.
• Write a utility script to find and replace existing tags that use spaces or upper-case characters with hyphens and lower-case characters.

I've not exhaustively checked the existing tags; it might be that we want some of them to be in upper case (perhaps proper nouns?). I could also believe this is inappropriate and/or confusing in some locales; I'm fairly confident it'd be safe for all en_* locales – so the vast majority of tags – but I could believe there are other locales where using hyphens instead of spaces and/or using exclusively lower-case characters would change meanings in a fundamental way.

Start with the linked defaultLocale.md tag guidance, then locate the CI validation scripts that run over pull requests. Done means validation rejects tags containing uppercase characters or spaces, and a separate utility can find and replace existing nonconforming tags while accounting for locale-specific concerns.