Move snippets outside of markdown

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

docs/tests/core-concepts/client/plans/file.cue

@@ -0,0 +1,15 @@
+import (
+	"encoding/yaml"
+	// ...
+)
+
+dagger.#Plan & {
+	client: filesystem: "config.yaml": write: {
+		// Convert a CUE value into a YAML formatted string
+		contents: yaml.Marshal(actions.pull.output.config)
+	}
+
+	actions: pull: docker.#Pull & {
+		source: "alpine"
+	}
+}