Document temporary workaround for Python 3.13

Refs #16

README.md

@@ -13,6 +13,15 @@ Install this plugin in the same environment as [LLM](https://llm.datasette.io/).
 ```bash
 llm install llm-claude-3
 ```
+
+The plugin may fail to install on **Python 3.13** due to a dependency problem. A temporary workaround for that problem is to run this:
+
+```bash
+llm install https://github.com/simonw/anthropic-sdk-python/archive/9c13bb441ee4eb88a100ed363fc431ec8fd30c43.zip
+llm install llm-claude-3
+```
+See [this issue](https://github.com/simonw/llm-claude-3/issues/16) for further details.
+
 ## Usage
 
 First, set [an API key](https://console.anthropic.com/settings/keys) for Claude 3: