Update issue templates

Author: suntong

.github/ISSUE_TEMPLATE/bug-report-template.md

@@ -0,0 +1,30 @@
+---
+name: Bug report template
+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**
+
+```sh
+$ echo "foo<br>bar" | html2md -i
+foo
+
+bar
+```
+
+**Expected output**
+
+```md
+foo
+bar
+```
+
+**Additional context**
+Add any other context about the problem here.