Update contributing and add package-manager (#3244)

Author: mattseddon

CONTRIBUTING.md

@@ -25,9 +25,9 @@ First, ensure that [Visual Studio Code](https://code.visualstudio.com) and
 - Open this repository as a project in VS Code and run `yarn install` from the
   _Integrated Terminal_.
 
-- Run `Tasks: Run Build Task` (Shift + Ctrl/Cmd + `b`) to start the extension
-  and Webview dev servers (alternatively, run `yarn dev-server` from the
-  _Terminal_). The latest build is saved in `extension/dist`.
+- Run `Tasks: Run Build Task` (Shift + Ctrl/Cmd + `b`) to start the individual
+  dev servers (alternatively, run `yarn dev-server` from the _Terminal_). The
+  latest build is saved in `extension/dist`.
 
   > **Warning**: Having a separate `.vsix` version of this extension installed
   > may cause all kinds of chaos in your dev env.

package.json

@@ -79,5 +79,6 @@
     "trim": "1.0.1",
     "vega-functions": "5.13.0",
     "vega-scale": "7.2.0"
-  }
+  },
+  "packageManager": "[email protected]"
 }