Add `sudo` added to the default Bash keywords.

[joshgoebel]

I'd like to see sudo added to the default Bash keywords. It's odd that it's not highlighted.

Originally posted by @mbomb007 in #3493 (comment)

[joshgoebel]

Perhaps built_in rather than keyword since right now keyword is JUST actual Bash keywords, but I'm totally open to this. PR welcome.