Add com_google_protobuf 3.19.0 (#20)

* Add com_google_protobuf 3.19.0

* Extract targets into a variable

modules/com_google_protobuf/metadata.json

diff --git a/modules/com_google_protobuf/metadata.json b/modules/com_google_protobuf/metadata.json
new file mode 100644
index 0000000..8039fb1
--- /dev/null
+++ b/modules/com_google_protobuf/metadata.json
@@ -0,0 +1,8 @@
+{
+    "homepage": "https://github.com/protocolbuffers/protobuf",
+    "maintainers": [],
+    "versions": [
+        "3.19.0"
+    ],
+    "yanked_versions": {}
+}