Add webhooks as a core plugin

Change-Id: Ib450f5815e9698aba2b6ffdbd85c69daea72ac24
diff --git a/.gitmodules b/.gitmodules
index 4797a7a..4ce7b5f 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -37,3 +37,8 @@
 	path = plugins/singleusergroup
 	url = ../plugins/singleusergroup
 	branch = .
+
+[submodule "plugins/webhooks"]
+	path = plugins/webhooks
+	url = ../plugins/webhooks
+	branch = .
diff --git a/plugins/webhooks b/plugins/webhooks
new file mode 160000
index 0000000..37b062e
--- /dev/null
+++ b/plugins/webhooks
@@ -0,0 +1 @@
+Subproject commit 37b062e08c5a83c4a939777cfddc9b6f97c44cdf
diff --git a/tools/bzl/plugins.bzl b/tools/bzl/plugins.bzl
index a42f4d5..4b4065f 100644
--- a/tools/bzl/plugins.bzl
+++ b/tools/bzl/plugins.bzl
@@ -7,6 +7,7 @@
     "replication",
     "reviewnotes",
     "singleusergroup",
+    "webhooks",
 ]
 
 CUSTOM_PLUGINS = [