Add benchmark suite & call it in CI

[djahandarie]

There are a couple of performance-related issues in the tracker, so I think it'd help the maturity of the project if we had a simple benchmark suite of a few of the most important top-level functions (db lookups, scans, popup generation with long amounts of text, etc) to start, so we could track improvements and regressions in our PRs.

Many of the things in test/ could probably be converted into benchmarks, though we'd likely need to adapt each of them to actually be working on a realistically large input for them to be representative of real-world usage.

References:

• https://github.com/benchmark-action/github-action-benchmark
• https://benchmarkjs.com/

[siikamiika]

I can try to do this

[Casheeew]

vitest supports bench functions: https://vitest.dev/api/#bench