In narrow links, escape single quotes

[gnprice]

When generating a link to a narrow (so in particular when ) and including any arbitrary strings like channel or topic names, we encode most characters other than ASCII letters.

We should expand the list to encode single quotes ('). For some software with heuristics for finding URLs in plain text, those can fool it into thinking that's the end of the URL.

Chat thread, with a user report and details on the current behavior:
#issues > inconsistent escaping in topic links

[gnprice]

We might also decide to treat star and bang (*, !) the same way; see chat thread.

Until that discussion is concluded, this issue is not ready for someone to work on. (Once that has concluded, I think we'll mark this issue "help wanted".)