feat: 增加单词打字练习功能并修复音频及空格对齐问题

[Tommy1109255]

由于雅思全面开始机考，对打字速度要求提升，所以我增加单词打字练习功能提升打字速度而且可以更好背单词

[hefengxian]

Thank you so much for your contribution! The idea is fantastic and adds great value to the project. While the initial implementation looked like a bit of 'vibe coding', the core concept is solid.

Based on your PR, I've made the following improvements: #48

1. UI/UX Refinement : Fixed several styling and layout issues (including word overflow and element positioning).
2. Audio Source : Switched the word pronunciation from browser speech synthesis to the project's native audio assets for better quality.

Great work on the creative side!

[hefengxian]

README updated

[hefengxian]

Fix the wrong mentioned user