Add issue template [skip ci] (#1410)

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,34 @@
+---
+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.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '....'
+3. Scroll down to '....'
+4. See error
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Environment (please complete the following information):**
+ - OS: [e.g. Ubuntu 20]
+ - OpenSSL version [e.g., 3.0.2]
+ - Compiler version used [e.g., clang 9.0.0]
+ - Build variables used [e.g., "-DOQS_ALGS_ENABLED=STD"]
+ - liboqs version [e.g. 0.7.2 or main branch]
+
+**Additional context**
+Add any other context about the problem here.