add github issue template.

.github/ISSUE_TEMPLATE

+<!--
+Thank you for reporting an issue.
+
+1. It's RECOMMENDED to submit PR for typo or tiny bug fix.
+2. If this's a FEATURE request, please provide: details, pseudo codes if necessary.
+3. If this's a BUG, please provide: course repetition, error log and configuration. Fill in as much of the template below as you're able.
+
+感谢您向我们反馈问题。
+
+1. 提交问题前，请先阅读 https://github.com/dotnetcore/CAP/wiki 上的文档。
+2. 我们推荐如果是小问题（错别字修改，小的 bug fix）直接提交 PR。
+3. 如果是一个新需求，请提供：详细需求描述，最好是有伪代码实现。
+4. 如果是一个 BUG，请提供：复现步骤，错误日志以及相关配置，并尽量填写下面的模板中的条目。
+6. 扩展阅读：[如何向开源项目提交无法解答的问题](https://zhuanlan.zhihu.com/p/25795393)
+-->
+
+Please answer these questions before submitting your issue.
+
+- Why do you submit this issue?
+- [ ] Question or discussion
+- [ ] Bug
+- [ ] Requirement
+- [ ] Feature or performance improvement
+
+___
+### Question
+- What do you want to know?
+
+___
+### Bug
+- Which version of SkyWalking, OS and JRE?
+
+- Which company or project?
+
+- What happen?
+If possible, provide a way for reproducing the error. e.g. demo application, component version.
+
+___
+### Requirement or improvement
+- Please describe about your requirements or improvement suggestions.
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