ci(github): add bug report issue template

Introduced alongside the first reported bug (#424) to standardize how
future issues are filed. The template mirrors the structure used in #424:
Description, Steps to Reproduce, Expected / Actual Behavior, Environment,
and an optional Possible Solution section.

Co-authored-by: Claude <noreply@anthropic.com>

Author: nanotaboada

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,40 @@
+---
+name: Bug report
+about: Report a bug or unexpected behavior
+title: "[BUG]"
+labels: bug, .NET
+assignees: ''
+
+---
+
+## Description
+
+A clear and concise description of what the bug is.
+
+## Steps to Reproduce
+
+1. Step 1
+2. Step 2
+3. Step 3
+
+## Expected Behavior
+
+What you expected to happen.
+
+## Actual Behavior
+
+What actually happened.
+
+## Environment
+
+- **.NET SDK version:** (output of `dotnet --version`)
+- **ASP.NET Core version:** (from `*.csproj`)
+- **OS:** (e.g., macOS 15.0, Ubuntu 24.04, Windows 11)
+
+## Additional Context
+
+Add any other context about the problem here (logs, screenshots, etc.).
+
+## Possible Solution
+
+(Optional) Suggest a fix or workaround if you have one.