Improve react example

Signed-off-by: Solomon Hykes <sh.github.6811@hykes.org>

examples/react/main.cue

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"dagger.io/netlify"
+	"dagger.io/yarn"
+	"dagger.io/git"
+)
+
+// Source code of the sample application
+repo: git.#Repository & {
+	remote: "https://github.com/kabirbaidhya/react-todo-app.git"
+	ref:    "624041b17bd62292143f99bce474a0e3c2d2dd61"
+}
+
+// Host the application with Netlify
+www: netlify.#Site & {
+	// Site name can be overridden
+	name: string | *"dagger-example-react"
+
+	// Deploy the output of yarn build
+	// (Netlify build feature is not used, to avoid extra cost).
+	contents: build
+}
+
+// Build the application with Yarn
+build: yarn.#Script & {
+	// What to build
+	source: repo
+
+	// How to build it (name of yarn script)
+	run: "build"
+}