ci(issue_template): 将问题反馈模板从markdown迁移到yaml格式

迁移问题反馈模板至yaml格式以利用GitHub表单功能，提升用户体验

.github/ISSUE_TEMPLATE/book_issue.yml

@@ -1,4 +1,3 @@
----
 name: Happy-LLM 问题反馈 / Textbook Issue Report
 description: 报告 Happy-LLM 中的代码/内容问题 / Report code/content issues in textbook
 title: "[问题/Issue] 章节X.X：简短问题描述 / ChapterX.X: Brief description"
@@ -64,5 +63,4 @@ body:
       description: 请确认以下事项 / Please confirm the following
       options:
         - label: 此问题未在过往Issue中被报告过 / This issue hasn't been reported before
-          required: true
----
+          required: true