Bit array int & float options on JavaScript

[richard-viney]

The following options related to floats and ints aren't yet supported in bit array patterns & expressions on the JavaScript target:

• Explicit size on floats, e.g. 32-bit. Currently floats are always 64-bit.
• Explicit endianness on floats and ints via big, little, and native. Currently values are always big endian.
• Explicit signedness on ints via signed and unsigned. Currently ints are always unsigned.

Other bit array segment options not yet supported on JavaScript are outside the scope of this issue, e.g.:

• The unit, utf16, utf16_codepoint, utf32, and utf32_codepoint options.
• The utf8_codepoint and utf8 options when used in patterns.
• Anything that's not byte-aligned.

I'm keen to implement this, so if there's any specific guidance or considerations that'd be great! I've played around today with adding size and endianness options to floats, so can extend that to ints and the other options listed above and submit for review.

[lpil]

Wonderful, yes! We want these for sure. I'm afraid I don't have any particular guidance.