Update bug report template description

Author: Bentroen

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,6 +1,6 @@
 ---
 name: Bug report
-about: Create a report to help us improve
+about: Report a bug to help us improve. Make sure to check the existing issues!
 title: ''
 labels: 'Type: Bug'
 assignees: ''