Document alternative authentication

Author: aron

README.md

@@ -43,6 +43,16 @@ export REPLICATE_API_TOKEN=<your token>
 
 We recommend not adding the token directly to your source code, because you don't want to put your credentials in source control. If anyone used your API key, their usage would be charged to your account.
 
+<details>
+
+<summary>Alternative authentication</summary>
+
+As of [replicate 1.0.5](https://github.com/replicate/replicate-python/releases/tag/1.0.5) and [cog 0.14.11](https://github.com/replicate/cog/releases/tag/v0.14.11) it is possible to pass a `REPLICATE_API_TOKEN` via the `context` as part of a prediction request.
+
+The `Replicate()` constructor will now use this context when available. This grants cog models the ability to use the Replicate client libraries, scoped to a user on a per request basis.
+
+</details>
+
 ## Run a model
 
 Create a new Python file and add the following code, replacing the model identifier and input with your own: