Add support for linking usernames.

Closes jaraco/skeleton#144

Author: jaraco

docs/conf.py

@@ -45,4 +45,13 @@
 # Preserve authored syntax for defaults
 autodoc_preserve_defaults = True
 
+# Add support for linking usernames, PyPI projects, Wikipedia pages
+github_url = 'https://github.com/'
+extlinks = {
+    'user': (f'{github_url}%s', '@%s'),
+    'pypi': ('https://pypi.org/project/%s', '%s'),
+    'wiki': ('https://wikipedia.org/wiki/%s', '%s'),
+}
+extensions += ['sphinx.ext.extlinks']
+
 # local