Add PullApprove support to enforce review

Ensure that OCI projects share the same approval settings.
opencontainers/project-template#4

Signed-off-by: Chris Aniszczyk <[email protected]>

Author: caniszczyk

.pullapprove.yml

@@ -0,0 +1,9 @@
+approve_by_comment: true
+approve_regex: ^LGTM
+reject_regex: ^Rejected
+reset_on_push: true
+reviewers:
+  teams:
+  - image-spec-maintainers
+  name: default
+  required: 2