Update issue templates

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Something is broken in the package
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+## Description
+
+A clear and concise description of what the bug is.
+
+## Steps to Reproduce
+
+Please describe how can the developers reproduce the problem in their own computers. Code snippets and sample input files are specially helpful. For example:
+
+1. Install the package
+2. Run the code below with the attached input file...
+3. The following error appears...
+
+## System Information
+ - Operating System: [e.g. Ubuntu 20.04]
+ - Python version: [e.g. 3.6]
+ - Solver: [e.g. Gurobi 9.0]
+ - Package version: [e.g. 0.1.0]