Add action to lock threads

[jsumners]

This PR adds a new GitHub Action that will run once per day and lock any issue or pull requests that have not had any activity in the prior 90 days. I opted for 90 days here out of an abundance of caution. We added this same action to Pino with a 30 day window. I'm not opposed to the 30 day window here.

The docs for the action can be found at -- https://github.com/dessant/lock-threads

This action will take a several days to process the current history due to -- https://github.com/dessant/lock-threads#why-are-only-some-issues-and-pull-requests-processed

We will see a lot of notifications that things have been locked. There's no way around that. We can speed up the initial processing by manually running the action through the Actions tab.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm