Restore the mkdocs watch list as src/ so serve reloads on source edits

mkdocstrings dropped its own watch hook in 0.23.0 in favour of MkDocs'
top-level watch:, so handlers.python.paths is not auto-watched. Without
this, editing anything under src/ during mkdocs serve would not trigger
a rebuild.

Author: maxisbey

mkdocs.yml

@@ -101,6 +101,9 @@ markdown_extensions:
       custom_checkbox: true
   - sane_lists # this means you can start a list from any number
 
+watch:
+  - src
+
 plugins:
   - search
   - social: