FR: Associated constants on CommandOptionValue for min/max values

[khionu]

I'm writing a parser for a command registration system, and it would be nice to have the bounds for min/max value/length available as constants.

I've not tested these numbers yet, I took them from MDN with the assumption that JS is the reason 53-bit values were the bound.

While the *_length fields don't use CommandOptionValue, I think it would be appropriate to put STRING_RANGE there for discoverability. I'm recommending the use of Range here for a few reasons:

1. Picking a name for "the minimum of the minimum value" etc is ugly
2. Range::contains is convenient
3. Range exposes the min/max as start and end fields, so the direct values are available

impl CommandOptionValue {
    const INTEGER_RANGE: Range<i64> = 
      -9007199254740991..=9007199254740991;
    const NUMBER_RANGE: Range<f64> =
      -9007199254740991.0..=9007199254740991.0;
    const STRING_RANGE: Range<u16> = 0..=6000;
}