Add bug report template

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,28 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: C-bug
+assignees: ''
+
+---
+
+<!-- Your issue may already be reported!
+Please search on the issue tracker before creating one. -->
+
+### Reproduction steps
+
+<!-- Ideally provide a key sequence and/or asciinema.org recording. --> 
+
+### Environment
+
+- Platform: <!--  macOS / Windows / Linux -->
+- Helix version: <!--  'hx -v' if using a release, 'git describe' if building from master -->
+
+<details><summary>~/.cache/helix/helix.log</summary>
+
+```
+please provide a copy of `~/.cache/helix/helix.log` here if possible, you may need to redact some of the lines
+```
+
+</details>