Create an alias for the sl command

[AvanBerne]

Summary

Make the adjustment in step 4 more fun by creating a small command to run instead of having to call the whole path.

Changes

Create the alias 'sl' for '/usr/games/sl' in the setup.sh file. Update the instruction for what to type in the terminal.

Closes: N/A

Task list

• [X] For workflow changes, I have verified the Actions workflows function as expected.
• [X] For content changes, I have reviewed the style guide.