Update issue templates

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
+IMPORTANT: Please use the following link to create a new issue. If your issue was not created using the app above, it will be closed immediately.
+
+注意：请按照下面的模板来新建 issue，不规范的 issue 会被立即关闭
+
+**Describe the bug**
+A clear description of what the bug is.
+
+**Screenshots**
+Add screenshots to help explain your problem.
+
+**Environment**
+ - Device: 
+ - Browser: 
+ - Vant Version: 
+
+**Reproduce**
+Provide the steps to reproduce and if possible a minimal demo of the problem via jsfiddle.
+https://jsfiddle.net/dfarLdko/1/