Document the type-refactor label (#1588)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: 3 people

triage/labels.rst

@@ -30,6 +30,8 @@ These labels are used to specify the type of issue:
   it is implicit that features are added to the ``main`` branch only.
   The `Ideas Discourse category`_ can be used to discuss enhancements
   before filing an issue.
+* :gh-label:`type-refactor`: for general code refactoring that
+  does not change user-facing behaviour.
 * :gh-label:`type-security`: for security issues.
   See also `Reporting security issues in Python`_.