Intro to Python (2021 Edition)

What's Changed

• 2021 Edition by @s2t2 in #62
• Run the App Exercise by @s2t2 in #63
• Unit 2 Prep by @s2t2 in #64
• Shopping Cart Support by @s2t2 in #67
• Update gspread package notes by @s2t2 in #68
• Developer Collaboration Exercise by @s2t2 in #70
• New Cleanup Exercise by @s2t2 in #72
• Web Service Updates - 2021 by @s2t2 in #74
• Freestyle Project - 2021 Updates by @s2t2 in #75
• Web App 2021 by @s2t2 in #76
• Web App Updates by @s2t2 in #83

Full Changelog: v2020...v2021