Implement Number.prototype.toFixed()

[HalidOdat]

This Pull Request fixes/closes #32.

This PR implements a WIP implementation of Number.prototype.toFixed(). This is a port of the official https://github.com/ulfjack/ryu/ repository's printf %f implementation, modified to comply to the Number.prototype.toFixed() behaviour.

Changes:

• Initial draft implementation of Number.prototype.toFixed()
• Added some tests

TODO:

• Figure out the max for Buffer size.
• Shrink the lookup tables, they are too big
  • Partially generate them, and compute some at runtime. The tables after shrinking them down with the method below. I think they are small enough now, I think Ill leave this for alter implementing other float to string conversions Implement Number.prototype.toExponential() #31 and Implement Number.prototype.toPrecision() #33
  • We probably only need a subset of the tables, because anything greater than 1e21 uses the default format and precision is clamped [0, 100]. We might be able to trim it.
    • Reduce POW10_SPLIT from 1224 to 8 (29184 bytes) ~99.35% reduction
    • Reduce POW10_SPLIT_2from 3133 to 481 (63648 bytes) ~84.65% reduction
• Add a bunch of tests
• Put under a feature flag

[Razican]

Looking good, I added some comments :)

[HalidOdat]

After a lot of testing this is ready for review/merge 🎉

[raskad]

From what I can see this look good. I'm not gonna pretend I understand all of the math behind this, but the code looks understandable to me.

[jedel1043]

LGTM! Just added some missing newlines that I'll commit with the reviews.

[jedel1043]

Oh, we didn't configure the queue for this repo. Let me open a PR for it.