Move issue template

Designate existing issue template as bug report template
and move to a hidden directory (.github/ISSUE_TEMPLATE/)
to enable multiple issue templates.

See https://help.github.com/en/articles/creating-issue-templates-for-your-repository

Author: Kieran O'Grady

ISSUE_TEMPLATE.md renamed to .github/ISSUE_TEMPLATE/bug_report.md

@@ -1,3 +1,12 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
 <!--
 
 Hi there! Here's a few pointers to help us help you with your issue as quickly