Add "Development task" to issue templates

Author: Mizu49

.github/ISSUE_TEMPLATE/development-task.md

@@ -0,0 +1,23 @@
+---
+name: Development task
+about: Task for next milestone and development goal!
+title: "[TASK]"
+labels: dev task
+assignees: ''
+
+---
+
+## Description of the task
+
+A clear and concise description of what we will be working on and how we will implement it. If possible, include the checklist for subtasks.
+
+- What kind of feature do we need.
+- How we should implement the feature.
+
+## Reference information
+
+If you have a resource that might help us to complete this task, please include that. Official documentation of Julia is preferable.
+
+## Additional context
+
+Add any other context or screenshots about the feature request here.