Player commands

[jwright159]

• Press tilde to open staff #9
• Press keys when staff open to play notes #11
• Played notes display on staff #13
• Add traditional ping command (pesterchum notif pattern) #15
• Add kill command with player entity selector (megalovania pattern) #42
• Basic player command functionality #118
• Animate staff opening and closing
• Display sharps
• Add short delay between recognizing pattern and executing command, where input is not accepted