feature: ability to add extra characters not to be encoded in url_encode

[DyfanJones]

Is there any plans in the future to allow extra characters not to be escaped? In python's urllib.parse.quote there is a parameter safe that allows extra characters not to be escaped (https://docs.python.org/3/library/urllib.parse.html#urllib.parse.quote).

My use case:
I am the current maintainer of a package called "paws". That creates a sdk for R to AWS. I need to be able to add the extra characters so that they don't get encoded. Here are the following modes requiring extra "safety".

encodeHost and encodeZone
][!$&'()*+,;=:<>"

encodePath
$&+,/;:=@

encodePathSegment
$&+:=@

encodeFragment
$&+,/;:=?@

See current implementation:
https://github.com/paws-r/paws/blob/01a9200a0c047607e667a211ce68d9653bb887b3/paws.common/R/url.R#L109-L149

I have managed to develop an R url encoder (https://github.com/paws-r/paws/blob/01a9200a0c047607e667a211ce68d9653bb887b3/paws.common/R/url.R#L151-L165). However it does suffer when the string needing to be encode scales up in size.

If this isn't in scope for urltools happy for you to close this.