Add upgrade note to README (#7937)

Closes #7858 

Co-authored-by: Zanie Blue <[email protected]>

Author: Aditya-PS-05

README.md

@@ -58,6 +58,12 @@ $ powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 |
 $ pip install uv
 ```
 
+If installed via the standalone installer, uv can update itself to the latest version:
+
+```console
+$ uv self update
+```
+
 See the [installation documentation](https://docs.astral.sh/uv/getting-started/installation/) for
 details and alternative installation methods.