Sigchainlib: Add OWNERS file

Test: m
Bug: 33166666
Change-Id: Ic4d695313e18adc31392cc1ab326a2ded0439d6d
diff --git a/sigchainlib/OWNERS b/sigchainlib/OWNERS
new file mode 100644
index 0000000..450fc12
--- /dev/null
+++ b/sigchainlib/OWNERS
@@ -0,0 +1,4 @@
+# Default maintainers and code reviewers:
+jmgao@google.com
+dimitry@google.com
+sehr@google.com