Update dockerfile and devcontainer.json to execute poststart.sh and forward x11

.devcontainer/devcontainer.json

@@ -4,6 +4,11 @@
       "dockerfile": "Dockerfile",
       "context": "."
     },
+    "postStartCommand": "./.devcontainer/poststart.sh",
+    "runArgs": [
+        "-e", "DISPLAY=${env:DISPLAY}",
+        "-v", "/tmp/.X11-unix:/tmp/.X11-unix"
+      ],
     "customizations": {
         "vscode": {
           "settings": {
@@ -14,7 +19,8 @@
             "ms-vscode.cpptools",
             "ms-vscode.makefile-tools",
             "androidtool.android",
-            "ms-azuretools.vscode-docker"
+            "ms-azuretools.vscode-docker",
+            "bbenoist.QML"
         ]
         }
       },