Add repository entry for bazel-contrib rules_kotlin (#1482)

.bcr/metadata.template.json

diff --git a/.bcr/metadata.template.json b/.bcr/metadata.template.json
index 6379769..40bc105 100644
--- a/.bcr/metadata.template.json
+++ b/.bcr/metadata.template.json
@@ -18,6 +18,7 @@
     }
   ],
   "repository": [
+    "github:bazel-contrib/rules_kotlin",
     "github:bazelbuild/rules_kotlin"
   ],
   "versions": [],