Merge pull request opencontainers#21 from wking/pullapprove-updates

.pullapprove.yml: Reset on push, ignore authors, and require sign-offs

Author: caniszczyk

.pullapprove.yml

@@ -1,7 +1,10 @@
 approve_by_comment: true
 approve_regex: ^LGTM
 reject_regex: ^Rejected
-reset_on_push: false
+reset_on_push: true
+author_approval: ignored
+signed_off_by:
+  required: true
 reviewers:
   teams:
   - tdc-maintainers