typing for semver version numbers

We are currently and more loosely assuming that it is a string currently. We should type this more strictly especially as we look to allow other versioning schemes.

The issue does not name a file, test, or entry point; begin by locating the TypeScript type currently used for semver version numbers. Done means that usage is no longer treated as an unrestricted string while preserving the stated path toward other versioning schemes.

Written by the indexing model from the issue text.