docs: Improve readme and code-of-conduct

[Ahzyuan]

Prep Steps

Before we dive in, let's confirm you've unlocked all these steps

• 🔍 I've checked for duplicate PRs (click to check)
• 📜 I've followed contribution guidelines
  • ✨ I've linted and formatted my code (how?)
  • 🔧 I've formatted the PR title appropriately (how?)
  • 🎯 I've targeted the master branch (how?)
  • 👐 I've allowed maintainer edits on my branch (how? → See step 6)
• 🛡️ I've added/updated tests to cover my changes if prossible (how?)
• 📝 I've added/updated the documentation for any new logic introduced (how?)
• ⏳ I understand @Ahzyuan has been busy lately and may need time to review. (we appreciate your patience!)

Type of changes

• 🐞 Bug fix
• 🌟 New feature
• 🧪 Tests
• 🏗 Refactoring
• ⚡ Performance improvement
• 📖 Documentation / docstrings
• ↩️ Revert
• 🧩 Other

Description

Purpose

This PR is for better README readability and repo management standardization.

Changes:

• README.md: fix typo in installation and add download badge.
• CODE_OF_CONDUCT.md: enhance the expression of our code of conduct