MAINTAINERS: add Documentation/dev-tools/ to workflows@

The goal of the workflows@ mailing list was to make it easier for
maintainers who don't use lore+lei to subscribe to topics related
to process changes. In other words it should cover changes to Documentation
files which most maintainers should know about. Recent changes from Kees [1]
to provide guidelines on naming KUnit files did not fall under workflows@
since Documentation/dev-tools/ isn't covered. The patch volume for
dev-tools isn't huge and most of the changes are interesting. Add it.

Link: https://lore.kernel.org/20240720165441.it.320-kees@kernel.org/ # [1]
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240723223258.2197852-1-kuba@kernel.org

MAINTAINERS

@@ -6711,6 +6711,7 @@ DOCUMENTATION PROCESS
 M:	Jonathan Corbet <corbet@lwn.net>
 L:	workflows@vger.kernel.org
 S:	Maintained
+F:	Documentation/dev-tools/
 F:	Documentation/maintainer/
 F:	Documentation/process/