[suggestion] Distinct color for command prefixes

[Dante-Broggi]

I recently came across this commit in the SerenityOS project:
Shell: Color bareword yellow if it's a prefix of at least one command
Which seems like a good idea for any color-using shell, and thus a good idea for fish to adopt.
As of version 3.6.1, fish does not treat command prefixes different from typo-ed commands, on MacOS Terminal.app.

> fish --version; echo $version
fish, version 3.6.1
3.6.1

  sh -c 'env HOME=$(mktemp -d) XDG_CONFIG_HOME= fish'

does not affect behavior in my environment.