github: skip URL handling for links under special site sections

Trending, events, collections, etc. are not real users and generate
"Not Found" if their URLs happen to match the format of e.g. a repo URL.
We can skip them and let the built-in title plugin do it.

Author: dgw

sopel_modules/github/github.py

@@ -49,7 +49,10 @@
 # GitHub enforces alphanumeric usernames, and allows only one punctuation character: hyphen ('-')
 # Regex copied and slightly modified to meet our needs from CC0 source:
 # https://github.com/shinnn/github-username-regex/blob/0794566cc10e8c5a0e562823f8f8e99fa044e5f4/module.js#L1
-githubUsername = r'[A-Za-z\d](?:[A-Za-z\d]|-(?=[A-Za-z\d])){0,38}'
+githubUsername = (
+    r'(?!(?:collections|events|sponsors|topics|trending)/)'  # exclude special sections
+    r'[A-Za-z\d](?:[A-Za-z\d]|-(?=[A-Za-z\d])){0,38}'
+)
 # GitHub additionally allows dots ('.') in repo names, as well as hyphens
 # not copied from anywhere, but handy to simply reuse
 githubRepoSlug = r'[A-Za-z0-9\.\-]+'