add two templates for issues

Author: SarahAlidoost

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,11 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is. If this issue is about a specific episode within a lesson, please provide its link or filename.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,14 @@
+---
+name: New lesson material
+about: Develop lessons
+title: ''
+labels: enhancement
+assignees: ''
+
+---
+
+**Short description of the diagnostic**
+Add a short description of the mterial that you would like to add.
+
+**Branch and pull request**
+Once you've started working, add the branch (and pull request) link.