Plotting additional metrics about authors

The [Author Directory](https://aclanthology.org/people/) has a nice plot of new authors per publication year, verified and unverified:

If they're not too difficult to make I would like to see 2 more plots on this page to help us understand the dynamics of authorship in our data:

1. Verification coverage by authorship: Number of namespecs that resolve to a verified vs. unverified person, by publication year.
2. Growth of our author database: Total verified and unverified authors in our database, measured every month starting Jan 2026.