Add a base zoom for clustering

Hello!

Currently there's a [base zoom option](https://github.com/mapbox/tippecanoe#dropping-a-fixed-fraction-of-features-by-zoom-level) for dropping features that stops dropping points beyond a given zoom level.

I tried to use it with clustering expecting no clusters beyond the specified base zoom, but it didn't work, clusters where still forming. So I guess it only applies to point dropping, and I couldn't find a base zoom option for clusters.

**Is it possible to add a base zoom option that prevents clustering beyond a given zoom level?**

Thank you for your time!

No files, tests, or entry points are named in the issue. Start by tracing the existing base zoom option and clustering behavior, then define done as preventing clusters from forming beyond the specified base zoom.

Written by the indexing model from the issue text.