Add Numerics library to docs

[cjsha]

I spent time searching how to generate random numbers in Bonsai, and I finally came across the Numerics library here. To help people find the Numerics library more quickly and easily, I feel that it would be helpful to point to it as a submodule here. I usually search the Bonsai docs first when I look for something new in Bonsai. I suspect others will try the same when doing random number generation which is probably a common operation in your userbase.

I don't know how y'all decide which packages go in the Bonsai docs though. Maybe it's not fully documented in the XML comments or something.

[banchan86]

Hey @cjsha!

So if I am not wrong, the current plan is to have documentation built in the package repository, but to have API/Reference docs pulled together for core packages at some point. They initially had everything together, but if I remember correctly there was a problem with the xrefmap being too large or slow to download. That seems to have been resolved but if we import everything as submodules I think there's also the issue with documentation building slowly. You did raise a good point too that there are missing XML doc comments for that package, so I think those need to be fixed as well before bringing them in. I have raised bonsai-rx/numerics#9 for the docfx website and bonsai-rx/numerics#10 for the XML doc comments.

edit: ah I found the DCM notes where this was discussed!
edit: also this PR referencing this as planned, as such I am closing this specific issue in favor of opening a general issue.