issue-template: add a new template for feature refinement

Signed-off-by: Louis Greiner <greiner.louis@gmail.com>

Author: louisgreiner

.github/ISSUE_TEMPLATE/3-refinement.md

@@ -0,0 +1,45 @@
+---
+name: Feature Ticket (refinement)
+about: Refinement about a future feature
+title: ""
+labels: ""
+assignees: ""
+---
+
+# Description
+
+<!-- Please give a brief description of the feature -->
+
+# Mock-ups
+
+<!-- Give a link to the mock-up or some screenshots -->
+
+# Acceptance Criteria
+
+<!-- A clear and exhaustive list of criteria / details that must be fulfilled -->
+
+- [ ] Criteria 1
+- [ ] Criteria 2
+- [ ] ...
+
+# Implementation Plan
+
+<!-- A clear and exhaustive list of steps to achieve this feature -->
+
+- Step 1
+- Step 2
+- ...
+
+# Tests
+
+# Definition of Ready
+
+- **PO/UX-UI**
+  - [ ] Mock-ups are complete and validated
+  - [ ] ACs are clear and have been reviewed by another refiner
+
+- **Technical**
+  - [ ] Implementation plan has been written and validated by another maintainer
+
+- **General**
+  - [ ] Validated by Adrian