Use a prelaunch task to build demo on debug

.vscode/launch.json

@@ -7,7 +7,8 @@
       "type": "extensionHost",
       "request": "launch",
       "runtimeExecutable": "${execPath}",
-      "args": ["--extensionDevelopmentPath=${workspaceRoot}/demo" ]
+      "args": ["--extensionDevelopmentPath=${workspaceRoot}/demo" ],
+      "preLaunchTask": "build"
     }
   ]
 }

.vscode/tasks.json

@@ -0,0 +1,14 @@
+{
+  "version": "0.1.0",
+  "command": "npm",
+  "isShellCommand": true,
+  "showOutput": "always",
+  "suppressTaskName": true,
+  "tasks": [
+    {
+      "isBuildCommand": true,
+      "taskName": "build",
+      "args": ["start"]
+    }
+  ]
+}

README.md

@@ -28,7 +28,7 @@ const colorSet: IColorSet = {
     color2: '#DA6771',
     color3: '#4EB071',
     color4: '#fff099',
-  },
+  }
 };
 generateTheme('My Theme', colorSet, path.join(__dirname, 'theme.json'));
 ```
@@ -50,9 +50,6 @@ Support below means that the standard VS Code grammar has explicit support for t
 
 ```bash
 npm run dev
-
-# In another shell
-npm start
 ```
 
-Them in VS Code press <kbd>F5</kbd> to launch the debugger with the generated theme available to switch to.
+Then in VS Code press <kbd>F5</kbd> to build demo and launch the debugger with the generated themes available to switch to.