Mention partial PRs in the contributing docs (#157863)
Adds a small new subsection to the section on contributing via coding that highlights the list of issues with partial patches that could be picked up by another contributor.
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e056956..454e16b 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -148,6 +148,14 @@
Please see the DevTools [CONTRIBUTING.md](https://github.com/flutter/devtools/blob/master/CONTRIBUTING.md)
guide to get started.
+### Helping with existing PRs
+
+Once you've learned the process of contributing, if you aren't sure what to work on next you
+might be interested in helping other developers complete their contributions by picking up an
+incomplete patch from the list of [issues with partial patches][has-partial-patch].
+
+[has-partial-patch]: https://github.com/flutter/flutter/labels/has%20partial%20patch
+
Outreach
--------
