Tidy-up templates

Tidy up the suppressions for markdownlint to make the templates render better in the GitHub UI.

Author: martincostello

.github/ISSUE_TEMPLATE.md

@@ -1,4 +1,7 @@
-<!-- markdownlint-disable MD041 -->
+---
+title: ''
+---
+
 ### Expected behaviour
 
 <!-- Explain what you expected to happen. -->

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,10 +1,10 @@
 ---
 name: Bug report
+title: Bug report
 about: Create a bug report to help us improve this project
 labels: bug
 ---
 
-<!-- markdownlint-disable MD041 -->
 ### Describe the bug
 
 <!--