Update issue templates

Author: cmbant

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,15 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is. 
+If you just want help, see the CosmoCoffee [help forum](https://cosmocoffee.info/viewforum.php?f=11) and [help assistant](https://cosmocoffee.info/help_assist.php).
+
+**To Reproduce**
+Steps to reproduce  (and platform if relevant). e.g. a complete python notebook.