To make it easier for external users of DMD to understand fully whether
a version of the database is compatible with the version of a given tool
- be it a first-class tool like `dmd-web`, or a custom integration, we
can add a helper method to do so.

This is also our first public function, which is part of our public API.

To make it easier to validate it works, as well as making it somewhat
self-documenting, we can make sure we have an example test.

We can use Hashicorp's `go-version` library to perform the version
comparisons.

As part of #532.