GitHub: Add bug report template

.github/ISSUE_TEMPLATE/bug-report.md

@@ -0,0 +1,30 @@
+---
+name: Bug Report
+about: Inform the maintainer about unexpected, reproducible behavior
+title: ''
+labels: bug
+assignees: dcommander
+
+---
+
+**Have you searched the existing issues (both open and closed) in the libjpeg-turbo issue tracker to ensure that this bug report is not a duplicate?**
+
+**Does this bug report describe one of the [two known and unsolvable issues with the JPEG format](https://libjpeg-turbo.org/pmwiki/uploads/About/TwoIssueswiththeJPEGStandard.pdf)?**
+
+**Clear and concise description of the bug:**
+
+**Steps to reproduce the bug (using *only* libjpeg-turbo):**
+
+**Image(s) needed in order to reproduce the bug (if applicable):**
+
+**Expected behavior:**
+
+**Observed behavior:**
+
+**Platform(s) (compiler version, operating system version, CPU) on which the bug was observed:**
+
+**libjpeg-turbo version(s) in which the bug was observed:**
+
+**If the bug is a regression, the specific commit that introduced the regression (use `git bisect` to determine this):**
+
+**Additional information:**