Stop tracking webapp/ref_webapp.egg-info/

setuptools regenerates this directory on every install, so keeping it in
the tree just produces spurious diffs whenever `pyproject.toml` changes.

Author: Nils Bars

.gitignore

@@ -17,6 +17,7 @@ webapp/.coverage
 webapp/.testmondata
 webapp/htmlcov/
 webapp/venv
+webapp/ref_webapp.egg-info/
 
 ref-docker-base/task-wrapper
 ref-docker-base/container-keys