Update issue and PR templates for consistency

Standardized the use of 'bug' (lowercase) in issue and pull request templates, updated icon for URL converter in config, and added quotes to placeholders in platform request template for improved clarity and consistency.

.github/pull_request_template.md

@@ -6,7 +6,7 @@
 
 <!-- 请勾选适用的改动类型 -->
 
-- [ ] 🐛 Bug 修复
+- [ ] 🐛 bug 修复
 - [ ] ✨ 新功能
 - [ ] 📝 文档更新
 - [ ] 🎨 代码风格/格式调整