Create issue template for bug reports

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,53 @@
+---
+name: Bug report
+about: Create a report to help us improve OpenCilk
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+### Describe the bug
+
+A clear and concise description of the bug.
+
+### Expected behavior
+
+What you expected to happen.
+
+### OpenCilk version
+
+- Release version: _[e.g., 1.0]_
+- Distribution method: _[e.g., `.sh` archive, Docker image, ...]_
+
+_-OR-_
+
+Built from source: 
+- `opencilk-project`: `branch` commit# (or tag)
+- `cheetah`: `branch` commit# (or tag)
+- `productivity-tools`: `branch` commit# (or tag)
+- `infrastructure`: `branch` commit# (or tag) _(if applicable)_
+
+### System information
+
+- OS: distribution, version _[e.g., Ubuntu 20.04]_
+- CPU: _[e.g., Intel Xeon Platinum 8260]_
+
+### Steps to reproduce (include relevant output)
+
+1. _[E.g., clone repo X]_
+
+2. _[E.g., build with parameters XYZ]_
+
+    Pass the `-v` flag to OpenCilk `clang`/`clang++` to show verbose compilation
+    commands and output.
+
+3. _[E.g., compiler crash output, runtime failure...]_
+
+### Working example code
+
+If applicable, include a working code example which triggers the bug.
+
+### Additional comments
+
+Add any other comments about the issue here.