Update readme for vscode instructions

README.md

 # New Project
 
-> ✨ Bootstrapped with Create Snowpack App (CSA).
+## How to start
+
+You can use any editor you like, but the following instructions lead to a 
+containerised dev environment using VSCode or Codium:
+
+Open VSCode and press `Ctrl+P`, then run:
+
+```
+ext install ms-vscode-remote.remote-containers
+```
+
+This installs an extension you can use to run dev environments from containers.
+It will run the VSCode backend inside the container so autocomplete, linting,
+introspection, etc. works with the version of the interpreter and dependencies
+used in production, and independent of those installed on your computer.
+
+Next: `Ctrl+P`, start typing: `Reopen in Container` and hit `Return`.
+
+You can now use any of the scripts defined in `package.json`, described below.
 
 ## Available Scripts
 
@@ -17,8 +35,6 @@ You will also see any lint errors in the console.
 Builds a static copy of your site to the `build/` folder.
 Your app is ready to be deployed!
 
-**For the best production performance:** Add a build bundler plugin like "@snowpack/plugin-webpack" to your `snowpack.config.js` config file.
-
 ### npm test
 
 Launches the application test runner.