chore(doc): change from GitPod (now ONA) to GitHub Codespaces (#6706)

.devcontainer/devcontainer.json

@@ -3,8 +3,9 @@
 {
 	"name": "edgetx-dev",
 	"image": "ghcr.io/edgetx/edgetx-dev:latest",
-	"runArgs": [ "--ipc=host"],
-
+	"runArgs": [
+		"--ipc=host"
+	],
 	// Add the IDs of extensions you want installed when the container is created.
 	"customizations": {
 		"vscode": {
@@ -12,5 +13,7 @@
 				"ms-vscode.cpptools"
 			]
 		}
-	}
+	},
+	// Post-create command to set up the environment
+	"postCreateCommand": "git submodule update --init --recursive && mkdir -p build && echo 'EdgeTX development environment ready!'"
 }