feat: implemented getters / setters and various string fns on Date

[ColinEberhardt]

This PR adds

• getters / setters for UTC dates (I don't plan to add any local-time related functionality)
• fromString, as a substitute for the new Date("2345-11-04") style constructor - I resisted the temptation to use as-regex for this task 😆
• toISOString

I've also modified Date.UTC so that it no longer calls out to the JS host.

[dcodeIO]

There may be an opportunity here to make fromString basically allocation-free, by walking the string and using strtol to extract the values (currently doesn't support a limit, though). @MaxGraey Thoughts?

[MaxGraey]

yeah, instead split better use indexOf + two substrings here

[dcodeIO]

Note that there would still be other avoidable allocations then when substringing the parts of interest into parseInt. Hence I thought this may be a case for slightly extending strtol so it stops at a given limit :)

[ColinEberhardt]

I'll leave this one to you @MaxGraey ;-)

[MaxGraey]

@ColinEberhardt ok =)

[bnbarak]

A tiny recommendations - add peace of mind for checking the odd corner cases in dates in different timezones. Perhaps add moment.js in devDependencies and add a test to compare the results of assemblyscript Date() type with moment.js Assuming moment.js is a source of truth to dates.

[ColinEberhardt]

A tiny recommendations - add peace of mind for checking the odd corner cases in dates in different timezones.

Thanks @bnbarak - I don't plan to add any timezone related functionality to Date, because JS dates are horrible! Instead I am implementing the Temporal spec here:

https://github.com/ColinEberhardt/assemblyscript-temporal

The only reason I am adding UTC-related Date functionality here is that because I need that for Temporal ;-)

[dcodeIO]

LGTM with the merge conflict fixed. We may also want to update the docs accordingly as a follow-up, and do a pass on String#split afterwards :)

[ColinEberhardt]

LGTM with the merge conflict fixed

Thanks @dcodeIO - rebased onto master - so should be good to merge when the tests pass 🤞

I'll update the docs after this is merged.