Add new repository entry to metadata template (#54)

Co-authored-by: Yun Peng <pcloudy@google.com>

.bcr/metadata.template.json

diff --git a/.bcr/metadata.template.json b/.bcr/metadata.template.json
index 7de9c0d..00958a3 100644
--- a/.bcr/metadata.template.json
+++ b/.bcr/metadata.template.json
@@ -13,6 +13,7 @@
         }
     ],
     "repository": [
+        "github:bazel-contrib/rules_shell",
         "github:bazelbuild/rules_shell"
     ],
     "versions": [],