Add some mentions of Codespaces for editing

This is minimally documented, merely indicating the presence of a
Codespaces configuration for now.

INSTALL.md

@@ -12,6 +12,11 @@ Use [`just run`](https://github.com/casey/just) to run the MkDocs server.
 
 This should install everything required.
 
+There is also a dev container setup that allows running the site in Codespaces
+or locally with VSCode and Docker.
+
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/opensafely/documentation)
+
 ### Inclusion of ehrQL documentation
 
 The ehrQL documentation is imported from the

README.md

@@ -4,6 +4,13 @@ This is the public documentation for using the [OpenSAFELY platform](https://www
 
 It provides information on how to get set up with and use the platform.
 
+## Running the site
+
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/opensafely/documentation)
+
+See INSTALL.md for more details,
+and for information on running locally instead of in Codespaces.
+
 ## Automated checks
 
 We have some automated checks that help us maintain the documentation.

docs/updating-the-docs.md

@@ -3,11 +3,19 @@ If you are an OpenSAFELY user and want to contribute corrections, clarifications
 You can either:
 
 * Suggest improvements in an [issue](https://github.com/opensafely/documentation/issues).
+* Run the documentation [in GitHub Codespaces](#running-in-codespaces) for editing.
 * Clone [the repo](https://github.com/opensafely/documentation) locally, make edits on a new branch, then create a pull request for it.
 * [Edit directly on GitHub](https://github.com/opensafely/documentation/tree/main/docs) ([instructions](https://docs.github.com/en/github/managing-files-in-a-repository/editing-files-in-your-repository)), making sure to "Create a new branch for this commit and start a pull request".
 
 Do not commit changes directly to the main branch.
 
+## Running in GitHub Codespaces
+
+Clicking the button below will open a codespace
+that allows you to run and edit the site.
+
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/opensafely/documentation)
+
 ## Documentation style
 
 When adding or revising text, use [Semantic Line Breaks](https://sembr.org/) rather than fixed length lines.