chore: add issue template

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,35 @@
+---
+name: Bug report
+about: Report something that isn't working.
+title: ''
+assignees: ''
+
+---
+
+<!--
+This is the chatmail core's bug report tracker.
+For Delta Chat feature requests and support, please go to the forum: https://support.delta.chat
+Please fill out as much of this form as you can (leaving out stuff that is not applicable is ok).
+-->
+
+- Operating System (Linux/Mac/Windows/iOS/Android):
+- Core Version: 
+- Client Version:
+
+## Expected behavior
+
+*What did you try to achieve?*
+
+## Actual behavior
+
+*What happened instead?*
+
+### Steps to reproduce the problem
+
+1. 
+2. 
+
+### Screenshots
+
+### Logs
+