Update issue templates

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve REBOUND
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+**Environment:**
+Which version of REBOUND are you using and on what operating System?
+ - REBOUND Version: [e.g. 28.7.0]
+ - API interface: [C or Python]
+ - Operating System (including version): [e.g. Linux, Windows, MacOS]
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+Describe the steps to reproduce the bug. Ideally this includes some or all of your C or Python code. It helps a lot if you trim down your code as much as possible. For example remove anything related to output and visualization if these are not relevant to the bug. 
+
+**Additional context**
+Add any other context about the problem here.