Move the license to the top level and add a contributing guide

CONTRIBUTING.md

@@ -0,0 +1,14 @@
+# Contributing to the Koto website
+
+Thank you for your interesting in contributing to the Koto website!
+
+## Improving documentation
+
+The source material for the website docs is maintained in the [Koto repository](https://github.com/koto-lang/koto/tree/main/crates/cli/docs), which is included here as a [submodule](./modules/koto). Versioned snapshots are maintained in [this repository](./website/content/docs/).
+
+It can be helpful to work on documentation improvements while seeing how they look on the website, and the following workflow is suggested:
+
+- Create a branch in the [Koto submodule](./modules/koto).
+- Changes to the docs should be made in the [docs folder](./modules/koto/crates/cli/docs/).
+- In the [website folder], run `just docs-watch` to automatically build the docs when files are changed. 
+- In another shell, run `just serve` to open the site in a browser. The site will be automatically refreshed when the docs are updated.