add devcontainer

flutter/.devcontainer/3.13.5/devcontainer.json

@@ -43,6 +43,6 @@
 	// Comment out to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
 	"remoteUser": "vscode",
 	"features": {
-		"docker-in-docker": "latest"
+		// "docker-in-docker": "latest"
 	}
 }

flutter/README.md

@@ -1,12 +1,19 @@
 # Flutter
 
 
+## Usage
 
-## devcontainer
+.devcontainer/Dockerfile
+```
+FROM jianboy/flutter-dev-container:3.13.5
+
+```
+
+## Develop
 
 ```
 docker login --username jianboy
 docker build  -f .devcontainer/Dockerfile2 -t jianboy/flutter-dev-container:3.13.5 .
 docker push jianboy/flutter-dev-container:3.13.5
 
-```
+```