📝 [doc] fix height of right content

[QJvic]

🤔 Nature of this PR

• [ ] 🐛 bug fix
• [ ] ✨ new feature
• [x] 📝 documentation improvement
• [ ] 🛝 demo code improvement
• [ ] 🚀 component style/interaction improvement
• [ ] 🏗️ ci/cd improvement
• [ ] ♻️ refactoring
• [ ] 🎨 code style optimization
• [ ] ✅ test cases
• [ ] 🔀 branch merging
• [ ] 💡 other

🔗 Related Issue

https://github.com/shuimo-design/shuimo-ui/issues/69

💡 Background and Solution

Set grid-template-rows: 100%; in .layout-main

✅ Pre-merge Checklist

❗️Please self-check and check all options.❗️

• [x] Documentation is supplemented or not needed
• [x] Code demonstration is provided or not needed
• [x] TypeScript definitions are supplemented or not needed
• [x] Changelog is provided or not needed