Use shallow clone for submodule

Jules-Bertholet · Jules-Bertholet · commit 2b0e30bab2e3 · 2021-05-21T14:41:59.000-04:00
diff --git a/.gitmodules b/.gitmodules
@@ -1,3 +1,5 @@
 [submodule "ckeditor5"]
 	path = ckeditor5
 	url = https://github.com/ckeditor/ckeditor5
+	update = checkout
+	shallow = true
