Parses the input string into an array of percentage or length values.
A length is a distance measurement, given as a number along with a unit which may be optional.
When a length is used in a style sheet or with a property in a ‘style’ attribute, the syntax must match the following pattern:
length ::= number (~"em" | ~"ex" | ~" px" | ~"in" | ~"cm" | ~"mm" | ~"pt" | ~"pc")?
When a length is used in an SVG presentation attribute, the syntax must match the following pattern:
length ::= number ("em" | "ex" | "px" | "in" | "cm" | "mm" | "pt" | "pc" | "%")?
Note that the non-property definition also allows a percentage unit identifier. The meaning of a percentage length value depends on the attribute for which the percentage length value has been specified. Two common cases are: (a) when a percentage length value represents a percentage of the viewport width or height, and (b) when a percentage length value represents a percentage of the bounding box width or height on a given object.