Add GitHub template (#27)

.github/ISSUE_TEMPLATE

+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 .NET Runtime?
+
+- 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.
\ No newline at end of file

.github/PULL_REQUEST_TEMPLATE

+Please answer these questions before submitting pull request
+
+- Why submit this pull request?
+- [ ] Bug fix
+- [ ] New feature provided
+- [ ] Improve performance
+
+- Related issues
+
+___
+### Bug fix
+- Bug description.
+
+- How to fix?
+
+___
+### New feature or improvement
+- Describe the details and related test reports.