Add stale PR policy (helm#1002)

* Add stale PR policy

* Add 1 week for stale label to be added

* fix typo

README.md

@@ -61,6 +61,9 @@ The following outlines the review procedure used by the Chart repository maintai
 * ***UX REVIEWED*** - The chart installation UX has been reviewed and found to be satisfactory. (may happen in parallel to CODE REVIEWED)
 * ***LGTM*** - Added ONLY once both UX/CODE reviewed are both present. Merge must be handled by someone OTHER than the maintainer that added the LGTM label. This label indicates that given a quick pass of the comments this change is ready to merge
 
+### Stale Pull Requests
+
+After initial review feedback, if no updates have been made to the pull request for 1 week, the `stale` label will be added. If after another week there are still no updates it will be closed. Please re-open if/when you have made the proper adjustments.
 
 ## Status of the Project