Case-insensitive prefix/suffix stripping

[stevengj]

@Palli

Neither works, but could be added, no breaking change, but my issue is that a straightforward extension is problematic. […] But this would miss some cases such as “hTtP”. I.e. there are exponentially many cases, here 16 to check for if chop functions aren’t made case-insensitive.

For that sort of thing you could use a regex: replace(s, r"^https?://"i => "") instead of chopprefix, for example.