Add instruction for how to upgrade slither in the CLI

README.md

@@ -76,6 +76,12 @@ If you're **not** going to use one of the [supported compilation frameworks](htt
 python3 -m pip install slither-analyzer
 ```
 
+If your slither version is behind the latest available release, you can upgrade slither to stay up to date with the latest features and bug fixes using the following command:
+
+```console
+pip install --upgrade slither-analyzer
+```
+
 ### Using Git
 
 ```bash