docs: Move chapter "Understanding Merge Conflicts" to Let's Contribute section

[CBID2]

Description

This PR does the following:

1. Move the "Understanding Merge Conflicts" chapter to the "Let's Contribute" file. This makes it easier for people to navigate the contributing files.
2. Removes the "Understanding Merge Conflicts" file for organizational purposes.
3. Removes the "Understanding Merge Conflicts" link from the sidebar.

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 #91

Mobile & Desktop Screenshots/Recordings

Added tests?

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

Added to documentation?

• [ ] 📜 README.md
• [ ] 📓 docs.opensauced.pizza
• [ ] 🍕 dev.to/opensauced
• [ ] 📕 storybook
• [X] 🙅 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?

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[CBID2]

Made the changes @adiati98

[CBID2]

Made the updates @adiati98

[adiati98]

Made the updates @adiati98

Awesome! Thanks, @CBID2! There's one more thing.

I run the intro locally, and there's still "Understanding merge conflicts" on the sidebar.

Can you please remove it? Thanks! 😊