Europa: integrate core packages, separate universe

Signed-off-by: Solomon Hykes <solomon@dagger.io>

europa-universe/examples/todoapp/base.cue

@@ -0,0 +1,28 @@
+// Deployment plan for Dagger's example todoapp
+package todoapp
+
+import (
+	"dagger.io/dagger"
+
+	"universe.dagger.io/git"
+	"universe.dagger.io/yarn"
+)
+
+dagger.#DAG & {
+	// Build the app with yarn
+	actions: build: yarn.#Build
+
+	// Wire up source code to build
+	{
+		input: directories: source: _
+		actions: build: source:     input.directories.source.contents
+	} | {
+		actions: {
+			pull: git.#Pull & {
+				remote: "https://github.com/mdn/todo-react"
+				ref:    "master"
+			}
+			build: source: pull.checkout
+		}
+	}
+}