Add puppet-vault-signers repository

Host the Go rewrites of the certmanager and sshsignhost Vault signing
helpers.

- Add config/git.unkin.net/unkin/repository/puppet-vault-signers.yaml
- Protect main with Owners-only merge and the standard woodpecker checks

config/git.unkin.net/unkin/repository/puppet-vault-signers.yaml

@@ -0,0 +1,14 @@
+description: "Go replacements for the certmanager and sshsignhost Vault signing helpers"
+private: false
+default_branch: "main"
+default_delete_branch_after_merge: true
+default_merge_style: "squash"
+branch_protection:
+  - rule_name: "main"
+    merge_whitelist_teams:
+      - "Owners"
+    enable_push: false
+    status_check_contexts:
+      - "ci/woodpecker/pr/build"
+      - "ci/woodpecker/pr/test"
+      - "ci/woodpecker/pr/pre-commit"