Create bug_report.md

Author: justin808

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+A bug is a crash or incorrect behavior. If you have a debugging or troubleshooting question, please open a discussion on the [Rails forum, category webpacker](https://discuss.rubyonrails.org/c/webpacker/10)
+
+Ruby version:
+Rails version:
+Webpacker version:
+
+Expected behavior:
+
+Actual behavior:
+
+Small, reproducible repo: