Add issue template

Author: Havret

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,22 @@
+---
+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.
+
+## Expected behavior
+A clear and concise description of what you expected to happen.
+
+## Environment:
+
+- OS: [OS name and version, e.g. Ubuntu 20.04]
+- Version: [NuGet package version of Protobuf.System.Text.Json or commit sha]
+
+## Additional context
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,30 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+## Feature description
+
+- Please provide the feature description in points.
+- What is the problem you're trying to solve?
+- What is in-scope and what is out-of-scope?
+
+## Feature in action
+
+```csharp
+// Most of the demos can be wrapped within short snippets of code
+```
+
+```csharp
+// If the code is spread across multiple files, please contain each one in a separate block
+```
+
+## Describe alternatives you've considered
+A clear and concise description of any alternative solutions or features you've considered.
+
+## Additional context
+Add any other context about the feature request here.