GitHub Issues: Create first issue template (Bug)

If we want people to use GH issues, we should
probably offer some issue templates to give
guidance on what to include.

Based on GH's standard bug template.

Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20221130133154.39454-2-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25589.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,25 @@
+---
+name: Bug report
+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**
+Steps to reproduce the behavior. Please make sure to not post any secrets like keys and passwords.
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Version information (please complete the following information):**
+ - OS: [e.g. Ubuntu 22.04]
+ - OpenVPN version: [e.g. 2.5.8]
+ - Repeat for peer if relevant
+
+**Additional context**
+Add any other context about the problem here.