Remove build before launch in launch.json

And update contributing with new instructions.

.vscode/launch.json

@@ -15,7 +15,6 @@
       "outFiles": [
         "${workspaceRoot}/extensions/ql-vscode/out/**/*.js",
       ],
-      "preLaunchTask": "Build",
       "env": {
         // uncomment to allow debugging the language server Java process from a remote java debugger
         // "DEBUG_LANGUAGE_SERVER": "true"
@@ -62,7 +61,6 @@
       "outFiles": [
         "${workspaceRoot}/extensions/ql-vscode/out/**/*.js",
       ],
-      "preLaunchTask": "Build"
     },
     {
       "name": "Launch Integration Tests - Minimal Workspace (vscode-codeql)",
@@ -79,7 +77,6 @@
       "outFiles": [
         "${workspaceRoot}/extensions/ql-vscode/out/**/*.js",
       ],
-      "preLaunchTask": "Build"
     }
   ]
 }

CONTRIBUTING.md

@@ -46,9 +46,18 @@ From the command line, go to the directory `extensions/ql-vscode` and run
 
 ```shell
 npm run build
+npm run watch
 ```
 
-Alternatively, you can build the extension within VS Code via `Terminal > Run Build Task...` (or `Ctrl+Shift+B` with the default key bindings).
+Alternatively, you can build the extension within VS Code via `Terminal > Run Build Task...` (or `Ctrl+Shift+B` with the default key bindings). And you can run the watch command via `Terminal > Run Task` and then select `npm watch` from the menu.
+
+Before running any of the launch commands, be sure to have run the `build` command to ensure that the JavaScript is compiled and the resources are copied to the proper location.
+
+We recommend that you keep`npm run watch` running in the backgound and you only need to re-run  `npm run build` in the following situations:
+
+1. on first checkout
+2. whenever any of the non-TypeScript resources have changed
+3. on any change to files included in the webview
 
 ### Installing the extension