Update requirements.

Reminding myself that Windows doesn't come with Git pre-installed.

README.md

@@ -21,6 +21,7 @@ Your `imatrix.txt` is expected to be located inside the `imatrix` folder. Includ
 Adjust `quantization_options` in **line 133**.
 
 **Requirements:**
+- Git
 - Python 3.11
   - `pip install huggingface_hub`