docs: add warning about DOMContentLoaded timing issue with Vite

[zxch3n]

Summary

• Added documentation warning about using DOMContentLoaded event with Loro in Vite
• Explained the timing conflict between DOMContentLoaded and ES module/WASM initialization
• Provided two solutions to resolve the issue

Context

When developers use DOMContentLoaded event listener with top-level Loro imports in Vite applications, the page fails to load. This is a common pattern developers might use, but it conflicts with how Vite loads ES modules asynchronously along with Loro's WASM initialization.

Problem Details

The issue occurs because:

1. Vite loads ES modules asynchronously
2. Loro's WASM module also initializes asynchronously
3. DOMContentLoaded may fire before these async operations complete
4. This results in the application failing silently with nothing rendered on screen

Changes

Added a collapsible warning section in the Getting Started guide that:

• Shows the problematic code pattern
• Explains why this timing issue occurs
• Provides two clear solutions:
  1. Remove the DOMContentLoaded listener (recommended)
  2. Use dynamic import inside the event listener

This will help developers avoid this common pitfall when integrating Loro with Vite projects.

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