Long doubles make histogram2d fail subtly, maybe add type check?

I'm experimenting with various optimizations in the pulsar search code in HENDRICS (https://github.com/StingraySoftware/HENDRICS/pull/65). One of my bottlenecks was a 2d histogram operation, and I gave a shot to yours. Tested with simulated data, everything worked and histogram2d was not a bottleneck anymore. Yay!
However...
When I used it on real data, Jupyter notebook was giving "dead kernel" messages with no information whatsoever. After spending one day banging my head, I tried to cast the longdouble arrays to `double`, and everything worked again.

It would help to add a type check, raising a ValueError or something similar if the number type is unsupported.

Start at the histogram2d entry point and reproduce the failure with longdouble arrays, comparing it with the working double-array case described in the issue. Done means unsupported numeric types are rejected with a clear ValueError instead of causing a dead kernel, while supported inputs continue to work.

Written by the indexing model from the issue text.