build: modularize the gulp file to be easier to maintain (#14259)

This is a precursor to bringing in some of the gulp tasks from angular.io,
which could lead to the gulpfile becoming unwieldy.

tools/gulp-tasks/serve.js

@@ -0,0 +1,33 @@
+module.exports = {
+
+  // Serve the built files
+  default: (gulp) => () => {
+    const connect = require('gulp-connect');
+    const cors = require('cors');
+    const path = require('path');
+
+    connect.server({
+      root: path.resolve(__dirname, '../../dist'),
+      port: 8000,
+      livereload: false,
+      open: false,
+      middleware: (connect, opt) => [cors()],
+    });
+  },
+
+  // Serve the examples
+  examples: (gulp) => () => {
+    const connect = require('gulp-connect');
+    const cors = require('cors');
+    const path = require('path');
+
+    connect.server({
+      root: path.resolve(__dirname, '../../dist/examples'),
+      port: 8001,
+      livereload: false,
+      open: false,
+      middleware: (connect, opt) => [cors()],
+    });
+  }
+
+};