website/cmd/highlight: Recognize more prompts in transcripts.
website/cmd/highlight: Recognize more prompts in transcripts.

Instead of a hardcoded "~> ", recognize anything starting with ~ or /, followed
by any non-spaces, and ending with "> ". This should cover most prompts as long
as the directory name doesn't contain spaces, and hopefully has no false
positive.

elves/elvish,elves/elvish,elves/elvish,elves/elvish,elves/elvish