Make issue template more eye-friendly

Notably by changing the h3 headings for bold text

ISSUE_TEMPLATE

@@ -1,7 +1,14 @@
-### Operating System or Device:
+**Operating system or device:**
 
-### Issue Description (what happened, and what was expected):
 
-### Steps to Reproduce:
 
-### Link to Minimal Example Project (Optional but very welcome):
+**Issue description** (what happened, and what was expected):
+
+
+
+**Steps to reproduce:**
+
+
+
+**Link to minimal example project** (optional but very welcome):
+