[ONOS-6375] Add skeleton code for Web GUI of mapping management app

Change-Id: I95079e6ac422591e6d5afed59b97d2a248573770
diff --git a/apps/mappingmanagement/web/src/main/resources/gui/css.html b/apps/mappingmanagement/web/src/main/resources/gui/css.html
new file mode 100644
index 0000000..7b22ae3
--- /dev/null
+++ b/apps/mappingmanagement/web/src/main/resources/gui/css.html
@@ -0,0 +1 @@
+<link rel="stylesheet" href="app/view/mapping/mapping.css">
\ No newline at end of file