Update bug report template (#3657)

.github/ISSUE_TEMPLATE/bug_report.md

@@ -7,36 +7,35 @@ assignees: ''
 
 ---
 
-**Describe the bug**
-A clear and concise description of what the bug is.
+## Describe the bug
+<!-- A clear and concise description of what the bug is. -->
 
-**To Reproduce**
-Steps to reproduce the behavior:
+## To reproduce
+<!-- Describe the steps to reproduce the behavior, e.g.:
 
 1. Go to '...'
 2. Click on '...'
 3. Compute '...'
 4. See error
+-->
 
-**Expected behavior**
-A clear and concise description of what you expected to happen.
+## Expected behavior
+<!-- If not obvious, describe what you expected to happen. -->
 
-**Screenshots**
-If applicable, add screenshots to help explain your problem.
-
-**System description (please complete the following information):**
+## Screenshots
+<!-- If applicable, add screenshots to help explain your problem. -->
 
+## System description
+<!--
 - Operating System: [e.g. Windows, Linux, ..., incl. version]
-- GRASS GIS version [e.g. 7.8.4]
-
-<!---
+- GRASS GIS version: [e.g. 4.0]
 
 - details about further software components
     - run `g.version -rge` in a GRASS GIS terminal session or check in
       the GUI menu "Help > About"
     - run `python3 -c "import sys, wx; print(sys.version); print(wx.version())"`
       to print the Python and wxPython version numbers
---->
+-->
 
-**Additional context**
-Add any other context about the problem here.
+## Additional context
+<!-- Add any other context about the problem. -->