Add issue template for bug report.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,50 @@
+---
+name: Bug report
+about: Create a report to help us improve.
+title: "[BUG]"
+labels: bug
+assignees: Alexhuszagh
+
+---
+
+## Description
+
+Please include a clear and concise description of the bug. Although very unlikely due to the nature of the project, if the bug includes a security vulnerability, please privately report the issue to the [maintainer](mailto:ahuszagh@gmail.com).
+
+## Prerequisites
+
+If applicable to the issue, here are a few things you should provide to help me understand the issue:
+
+- Qt version: [5, 6]
+- Extension: [Advanced Docking System, ...]
+- Theme: [Dark, Light, Dark-Purple, ...]
+
+## Test case
+
+Please provide a short, complete (with widgets, etc) test case for
+the issue, showing clearly the expected and obtained results.
+
+Example test case:
+
+```python
+import sys
+from PyQt6 import QtCore, QtGui, QtWidgets
+
+QtCore.QDir.addSearchPath('dark', f'dist/pyqt6/dark/')
+
+if __name__ == '__main__':
+    app = QtWidgets.QApplication(sys.argv)
+    file = QtCore.QFile('dark:stylesheet.qss')
+    file.open(
+        QtCore.QFile.OpenModeFlag.ReadOnly | 
+        QtCore.QFile.OpenModeFlag.Text
+    )
+    stream = QtCore.QTextStream(file)
+    app.setStyleSheet(stream.readAll())
+
+    dialog = QtWidgets.QFileDialog()
+    dialog.setFileMode(QtWidgets.QFileDialog.FileMode.Directory)
+    dialog.exec()
+
+    app.quit()
+```