Automated checks to prevent use of "latest" tag in drivers

[kimdhamilton]

As discussed in #400, we're no longer allowing drivers to be submitted with the "latest" tag. For now, we are addressing this in the following ways:

• Update guidance: https://github.com/decentralized-identity/universal-resolver/pull/398
• Enforce with code review

It would be ideal to add an automated check via github actions or similar to help with enforcement