Add probot configuration file (exercism#412)

stkent · jtigger · commit 0ac6f639a71d · 2017-04-14T09:38:13.000-04:00
Initial configuration specifies that "first-timers only" issues should
be exempt from cleanup.
diff --git a/.github/stale.yml b/.github/stale.yml
@@ -0,0 +1,8 @@
+# Issues or Pull Requests with these labels will never be considered stale
+exemptLabels:
+  - "first-timers only"
+  - "good first patch"
+  - "policy"
+
+# Label to use when marking as stale
+staleLabel: stale
