Add test for docker example

Signed-off-by: Tom Chauveau <tom.chauveau@epitech.eu>

tests/stdlib/docker/pull/pull.cue

@@ -0,0 +1,27 @@
+package docker
+
+import (
+	"dagger.io/dagger/op"
+	"dagger.io/docker"
+)
+
+TestImageFromRegistry: {
+	image: docker.#Pull & {
+		from: "index.docker.io/the0only0vasek/alpine-test"
+	}
+
+	verify: #up: [
+		op.#Load & {
+			from: image
+		},
+
+		op.#Exec & {
+			always: true
+			args: [
+				"sh", "-c", """
+						grep -q "test" /test.txt
+					""",
+			]
+		},
+	]
+}