fix: file path is not an absolute path when startswith "#"

[YourWildDad]

What:

I don't know why this function thinks that the path starting with '#' an absolute path, but according to the definition of absolute path, this is wrong, and the path name starting with '#' return false in the built-in functions in many languages

Why:

Same as nodejs built-in implementation require('path').isAbsolute(). The file path starting with '#' is not an absolute path.

How:

Modify the regular expression to remove the match at the starting of '#'

Checklist:

• Documentation
• Added/updated unit tests
• Code complete

[matthew-dean]

Is there a real-world use case where this has caused a problem? In Less, this function determines if the URL should be re-written, which a URL starting with # would not.