optimise the req regex

[JakeChampion]

This was optimised by the regexp-tree-cli package like so:

> npx regexp-tree-cli -o -e '/\s*(?:\{(.*)\})?\s*(?:(\$?[^\s]+))?\s*(?:\[([^\]]*)\])?\s*(?:-?\s*([\s\S]*))\s*$/'
 Optimized: /\s*(?:{(.*)})?\s*(?:(\$?\S+))?\s*(?:\[([^\]]*)])?\s*-?\s*([\S\s]*)\s*$/

[coveralls]

Coverage remained the same at 94.752% when pulling 133e490 on JakeChampion:patch-1 into 8aab533 on SassDoc:master.

[pascalduez]

Hi @JakeChampion,

interesting.
Could you provide a bit more insight on why this would be beneficial, what are you trying to fix or improve etc. ?

[JakeChampion]

The original regex was harder to read due to all the extra escaping of characters which didn't need to be escaped.

[pascalduez]

Thanks!