Include the 'Belt' standard library

[austindd]

Since BuckleScript officially ships with Belt as an alternative standard library (and officially recommends its use), Belt should be available in ReBench.

I am not sure how to go about integrating it at this time, but it would be a very welcomed improvement!

[glennsl]

This uses bs-in-a-box and is just a matter of replacing the vendored compiler and stdlib bundle there as long as the interface is still the same. Unfortunately I suspect it's not. I also think the process of building it has changed a lot.

I think @ryyppy and @thangngoc89 know the process best these days. Maybe they can chime in, or have plans to do something similar to this elsewhere.

[thangngoc89]

@glennsl I totally forgot about rebench, i’ll see if I can update this

[tsnobip]

I agree, rebench is so useful to quickly benchmark BS code, having access to Belt would be a game changer because Belt implementation usually makes it much faster than the JS lib and a bit faster than Stdlib.

I don't know if things have become a bit easier to integrate since last year, I know there's some ongoing work with a new playground for reasonml.org, maybe some of the efforts could be reused here.