Also add note about using -W clippy::lint_group

Author: phansch

README.md

@@ -149,7 +149,7 @@ You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
 
 Note: `deny` produces errors instead of warnings.
 
-If you do not want to include your lint levels in your code, you can globally enable/disable lints by passing extra flags to clippy during the run: `cargo clippy -- -A clippy::lint_name` will run clippy with `lint_name` disabled and `cargo clippy -- -W clippy::lint_name` will run it with that enabled.
+If you do not want to include your lint levels in your code, you can globally enable/disable lints by passing extra flags to clippy during the run: `cargo clippy -- -A clippy::lint_name` will run clippy with `lint_name` disabled and `cargo clippy -- -W clippy::lint_name` will run it with that enabled. This also works with lint groups. For example you can run Clippy with warnings for all lints enabled: `cargo clippy -- -W clippy::pedantic`
 
 ## License