docs: Document ZED_DEVELOPMENT_AUTH (#23571)

This PR adds documentation for the `ZED_DEVELOPMENT_AUTH` environment
variable, in the hopes that it helps folks find it sooner.

Release Notes:

- N/A

docs/src/development.md

@@ -10,6 +10,30 @@ If you'd like to develop collaboration features, additionally see:
 
 - [Local Collaboration](./development/local-collaboration.md)
 
+## Authentication
+
+When developing Zed you will typically want to sign in to the production collab
+instance, unless you are specifically working on features that require running
+collab locally.
+
+In order to bypass the keychain prompts that pop up when trying to sign in each
+time you run a development build of Zed, you can use the development auth
+provider.
+
+This will store your Zed access token in a local file on disk that can be read
+in development, bypassing the need to retrieve the credential from the system
+keychain.
+
+To enable the development auth provider, set this in your shell:
+
+```
+ZED_DEVELOPMENT_AUTH=1
+```
+
+You may want to add this to your shell profile so you don't need to remember to enable it each time.
+
+> Note: This only works for development builds. It is a no-op in all non-development release channels.
+
 ## Contributor links
 
 - [CONTRIBUTING.md](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md)