[修订] 修订 Skript 教程并完善文档

[Radiation-pi]

对 Skript 基础与高级教程进行了全面扩展与内容优化，主要包括：

修改了错误的例子，新增了一些对 Java 的基础知识补充，提升初学者引导，降低入门难度
补充例子和练习，提供更多 Skript 可参考的代码；
更新配图示例并重构内容排布，强化可读性与学习路径连贯性；
按照格式规范进行格式修改，避免在标题中大量使用斜体和引用等不规范用法。

至此，Skript 部分已经处于可读状态。

[TODO] Skript Addon 的编写和一些好用的 Skript 片段以供参考

[Copilot]

Pull request overview

This PR provides a comprehensive revision and expansion of the Skript tutorial documentation in Chinese. The changes transform the documentation from an "unreadable" state to a well-structured, comprehensive learning resource for both beginners and advanced users.

Key Changes:

• Corrected erroneous examples and added Java fundamentals to lower the barrier to entry
• Expanded practice exercises with more reference code examples
• Updated diagrams and restructured content layout to improve readability and learning flow
• Standardized formatting to avoid irregular use of italics and quotes in headings

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 3 comments.

File	Description
skript.md	Updated introduction, added detailed download links for Skript core, addons, scripts, and snippets; improved performance explanation section
basic-tutorials.md	Massively expanded from basic concepts to detailed tutorials covering events, commands, variables, arrays, loops, and functions with multiple practice exercises
advanced-tutorials.md	Enhanced skript-reflect documentation with better Java basics explanation, improved examples, and clearer structure for advanced topics
_images/SkriptBasic1.png	Added new screenshot image for documentation

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