add some local dev instructions to the readme

README.md

@@ -9,3 +9,26 @@ It includes support for running Framework data loaders with the following langua
 - R 4.3
 - duckdb 0.10.1
 - Rust 1.77
+
+## Usage
+
+This will be published on a public repository soon. In the mean time, please use the local development instructions below.
+
+## Local development
+
+From this repository, run
+
+```
+yarn install
+yarn build
+```
+
+This will install dependencies needed for the repository, and build the image.
+
+To run the image, you can use the command
+
+```
+docker run -it observablehq/framework-runtime:latest bash
+```
+
+This will launch a shell in the runtime environment. From here you should be able to clone repositories, use `npm init @observablehq`, and otherwise interact with Framework projects. Not that after exiting the shell any files you worked with will be lost. Consider using [Docker Volumes](https://docs.docker.com/storage/volumes/) if you want a persistent environment.