docs(README): update

README.md

@@ -1,7 +1,21 @@
 # Stencila VSCode Extension Demo
 
-Welcome to the demo workspace for the Stencila VSCode extension 🎉!
+## Launching the demo
 
-::: create code to print current time
+Welcome to the demo GitHub Codespace for the Stencila VSCode extension. You can launch the demo, in a data center near you, by clicking this button:
 
-:::
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/stencila/demo-codespace)
+
+## Interactive walkthroughs
+
+When the Codespace is open we recommend trying one of our interactive walkthroughs. Press <kbd>F2</kbd> to bring up the Stencila command palette and select from one of the walkthroughs.
+
+## Installed languages and packages
+
+This Codespace include Python and R with popular data science packages installed:
+
+- Python: `numpy`, `matplotlib`, `pandas`, `requests`
+
+- R: `tidyverse`
+
+If you'd like to try this demo with other languages or packages [create an issue](https://github.com/stencila/demo-codespace/issues/new), or submit a PR with changes to the [Dockerfile](https://github.com/stencila/demo-codespace/edit/main/.devcontainer/Dockerfile).