Add tests for bigfraction.js round()

[andrefs]

I've added 3 tests:

1. One with a big numerator, previously complained about Infinity, now ok ✔️
2. One with big numerator and denominator, previously complained about NaN (due to attempted division of Infinitys), now ok ✔️
3. One with a big places, which is now failing ❎ Not sure whether supporting BigInt places is a reasonable use case 😅

[infusion]

I wouldn't go beyond reasonable decimal places count. I can't think of a use case for that.

Why do you expect your 3rd case with "'409652136432929109317'.repeat(100) / 10" to be -1 and not '409652136432929109317'.repeat(99) + '40965213643292910932'

[infusion]

I added those two working test cases. The case with many decimal places ca be worked out when someone has a use case for it :D

[andrefs]

Why do you expect your 3rd case with "'409652136432929109317'.repeat(100) / 10" to be -1

Nevermind, I forgot to update it when I copied it from another test case

The case with many decimal places ca be worked out when someone has a use case for it :D

Sounds cool, thanks, this was great! 😎

[infusion]

Thanks for bringing this up!