Add autofix bot STS policy (#68)

Signed-off-by: Nghia Tran <tcnghia@gmail.com>

Author: tcnghia

.github/chainguard/autofix.sts.yaml

@@ -0,0 +1,10 @@
+issuer: https://accounts.google.com
+# autofix@prod-enforce-fabc.iam.gserviceaccount.com
+subject: "114301252256317020592"
+
+permissions:
+  checks: write
+  contents: write
+  pull_requests: read
+  statuses: read
+  workflows: write # Allow triggering actions when authoring commits.