Added devcontainer docs

Author: Fordi

README.md

@@ -89,6 +89,7 @@ no-as-service/
 ├── index.js            # Express API
 ├── reasons.json        # 1000+ universal rejection reasons
 ├── package.json
+├── .devcontainer.json  # VS Code / Github devcontainer setup
 └── README.md
 ```
 
@@ -118,6 +119,10 @@ For reference, here’s the package config:
 
 ---
 
+## ⚓ Devcontainer
+
+If you open this repo in Github Codespaces, it will automatically use `.devcontainer.json` to set up your environment.  If you open it in VSCode, it will ask you if you want to reopen it in a container.
+
 ## 👤 Author
 
 Created with creative stubbornness by [hotheadhacker](https://github.com/hotheadhacker)