feat: add stale config (#19)

This commit adds configuration for the stale bot to automatically mark
question issues as stale and close them after some time passes. Note it
won't currently automatically do anything with non-question issues

.github/stale.yml

@@ -0,0 +1,25 @@
+# Configuration for probot-stale - https://github.com/probot/stale
+
+issues:
+  # Number of days of inactivity before an Issue or Pull Request becomes stale
+  daysUntilStale: 7 
+
+  # Number of days of inactivity before an Issue or Pull Request with the stale label is closed.
+  # Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
+  daysUntilClose: 7
+
+  # Only issues or pull requests with all of these labels are check if stale. Defaults to `[]` (disabled)
+  onlyLabels:
+    - question
+    - autoclose
+
+  # Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
+  exemptLabels:
+    - p0
+    - bug
+
+  # Comment to post when marking as stale. Set to `false` to disable
+  markComment: >
+    This issue has been automatically marked as stale because it has not had
+    recent activity. It will be closed if no further activity occurs. Thank you
+    for your contributions.