Allow tracking runs/official while ignoring other runs dirs

Author: sjarmak

.gitignore

@@ -17,6 +17,10 @@ archive/
 jobs/
 results/
 runs/
+!runs/
+runs/*
+!runs/official/
+!runs/official/**
 tasks/
 # Keep published official-results pages tracked.
 !docs/official_results/runs/