Use demo icons instead of mdi (#2623)

* generate demo icons

* replace tab icons and update build file

* review comments

* review comments

* update ignores

* cleanup

demo/script/gen-icons.js

@@ -0,0 +1,15 @@
+#!/usr/bin/env node
+const fs = require("fs");
+const {
+  findIcons,
+  generateIconset,
+  genMDIIcons,
+} = require("../../gulp/tasks/gen-icons.js");
+
+function genHademoIcons() {
+  const iconNames = findIcons("./src", "hademo");
+  fs.writeFileSync("./hademo-icons.html", generateIconset("hademo", iconNames));
+}
+
+genMDIIcons();
+genHademoIcons();