chore: add lock threads robot config (#2918)

ref #2889

.github/lock.yml

@@ -0,0 +1,14 @@
+# Configuration for lock-threads - https://github.com/dessant/lock-threads
+
+# Number of days of inactivity before a closed issue or pull request is locked
+daysUntilLock: 365
+# Comment to post before locking. Set to `false` to disable
+lockComment: >
+  This thread has been automatically locked because it has not had recent
+  activity. Please open a new issue for related bugs and link to relevant
+  comments in this thread.
+# Issues or pull requests with these labels will not be locked
+# exemptLabels:
+#   - no-locking
+# Limit to only `issues` or `pulls`
+only: issues