I wanted to add myself as a watcher of all things Linux-related and I noticed we have several linux watchlist definitions already (eg. linux_sandboxing, linux_seccomp_bpf, linux_fonts).

It would be nice if we could create a 'linux' watchlist group that has all of those so I could just add myself as a watcher of 'linux'.  If someone else wanted to watch all of the Linux stuff, they wouldn't have to duplicate everything.