docs: updating contributing section in README

[jdwilkin4]

Description

This PR is responsible for updating the README file to include the correct instructions for how to contribute. Previously, the README mentioned folders that were not in existence in the repo. I updated the contribute section so contributions know to edit the pizza-facts.md and pizza-recipes.md files.

What type of PR is this? (check all applicable)

• [ ] 🍕 Feature
• [ ] 🐛 Bug Fix
• [x] 📝 Documentation Update
• [ ] 🎨 Style
• [ ] 🧑‍💻 Code Refactor
• [ ] 🔥 Performance Improvements
• [ ] ✅ Test
• [ ] 🤖 Build
• [ ] 🔁 CI
• [ ] 📦 Chore (Release)
• [ ] ⏩ Revert

Related Tickets & Documents

closes #2

Added tests?

• [ ] 👍 yes
• [x] 🙅 no, because they aren't needed
• [ ] 🙋 no, because I need help

Added to documentation?

• [x] 📜 README.md
• [ ] 📓 docs.opensauced.pizza
• [ ] 🍕 dev.to/opensauced
• [ ] 📕 storybook
• [ ] 🙅 no documentation needed

[optional] Are there any post-deployment tasks we need to perform?

[optional] What gif best describes this PR or how it makes you feel?

[BekahHW]