Modify plugins:core to build codemirror-editor

Bug: Issue 4437
Change-Id: I6ca6049f5371515e0891e7e334dc66bd9c12167e
diff --git a/.gitmodules b/.gitmodules
index ec8afee..8d75bcc 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,8 @@
+[submodule "plugins/codemirror-editor"]
+	path = plugins/codemirror-editor
+	url = ../plugins/codemirror-editor
+	branch = .
+
 [submodule "plugins/commit-message-length-validator"]
 	path = plugins/commit-message-length-validator
 	url = ../plugins/commit-message-length-validator