add design template

Author: chenyukang

.github/ISSUE_TEMPLATE/design.md

@@ -0,0 +1,19 @@
+---
+name: Project design
+about: Suggest an idea for this project
+title: ''
+labels: 'design'
+assignees: ''
+
+---
+
+**Goal or context for the feature**
+- A clear and concise description of what the problem is.
+
+**Describe the solution you'd like**
+- A clear and concise description of the solution.
+- Reference links
+- Describe alternatives you've considered
+
+**Focused testing scope**
+Describe the main testing area