bashcrawl errata for Mac users

[zstumgoren]

We need an errata note for the Bashcrawl assignment related to the potions spell, which asks users to colorize the ls command by setting a new alias ls=‘ls -F --color=auto’. This leads to an error on Mac:

~/code/bashcrawl/entrance/cellar/armoury/chamber/portal/library> ls -F --color=auto
ls: illegal option -- -
usage: ls [-@ABCFGHLOPRSTUWabcdefghiklmnopqrstuwx1%] [file ...]

Don't see this issue mentioned in the Bashcrawl issues but the --color flag was apparently replaced by the-G flag on Macs many years ago, so it appears the proper alias should be alias ls='ls -FG.

We should verify with Mac users in class to make sure this works for everyone. May need to also explore an edge case related to --color flag based on this SO post.