Update issue templates

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+### Describe the bug
+A clear and concise description of what the bug is.
+
+### Which project is your bug related to?
+- [x] Client
+- [ ] ManagedClient
+- [ ] MQTTnet.Server standalone
+- [ ] Server
+- [ ] Generic
+
+### To Reproduce
+Steps to reproduce the behavior:
+1. Using this version of MQTTnet '...'.
+2. Run this code '....'.
+3. With these arguments '....'.
+4. See error.
+
+### Expected behavior
+A clear and concise description of what you expected to happen.
+
+### Screenshots
+If applicable, add screenshots to help explain your problem.
+
+### Additional context / logging
+Add any other context about the problem here.
+Include debugging or logging information here:
+
+```batch
+```
+### Code example
+ Please provide full code examples below where possible to make it easier for the developers to check your issues.
+ 
+```csharp
+```