support optional whitespace between the value and units

[beforan]

The current regex already doesn't allow for whitespace forming part of either the <number> or <units> segments so this should be trivial.

For the original intended use case, no space makes sense, e.g. working with strings like "50em" or "10px".

However the parse-unit example is "50 gold" and having a space is perfectly reasonable there.

So for added utility we should allow (but not require) whitespace in input strings with units (i.e. in parseString().

[beforan]

just realised 50em is a terrifying example value, but whatever. yolo.

[beforan]

i guess toString() will want to act on an option to include whitespace or not?

[beforan]

accepting whitespace should be done, just need to add a "separator" property that .toString() and .toArray() can use for their output.

[beforan]

accepting whitespace in strings for parse() and parseString() works and is unit tested in 1.0.0

supporting whitespace (or other) separators in outputs (toString(), toArray()) will happen in 1.1.0