Add outputs.files task to plan

Signed-off-by: Helder Correia <174525+helderco@users.noreply.github.com>

tests/plan/outputs/files/no_contents.cue

@@ -0,0 +1,7 @@
+package main
+
+import "dagger.io/dagger"
+
+dagger.#Plan & {
+	outputs: files: test: dest: "./test"
+}