Refactor section headers in bug_report.md

Updated section headers in bug report template for consistency.

Author: fenbox

.github/ISSUE_TEMPLATE/bug_report.md

@@ -12,7 +12,7 @@ assignees: ''
 
 A clear and concise description of what the bug is.
 
-### To Reproduce
+## To Reproduce
 
 Steps to reproduce the behavior:
 
@@ -21,15 +21,15 @@ Steps to reproduce the behavior:
 3. Scroll down to '....'
 4. See error
 
-### Expected behavior
+## Expected behavior
 
 A clear and concise description of what you expected to happen.
 
-### Screenshots
+## Screenshots
 
 If applicable, add screenshots or video to help explain your problem.
 
-### Platform
+## Platform
 
 - Device: [e.g. Desktop, Mobile]
 - OS: [e.g. macOS]