Added bug report template

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,27 @@
+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
+<!-- Below, please describe what the Bug does in one or two short sentences. -->
+## Description
+
+<!-- Below describe the steps necessary to reproduce the malicious behaviour -->
+## Reproducing
+
+<!-- Below, please describe what Zettlr should do instead -->
+## Expected behaviour
+
+<!-- If helpful, add Screenshots to further narrow down the issue -->
+**Screenshots**
+
+<!-- Please provide information on your operating system -->
+## Platform
+ - OS: [e.g. iOS]
+ - OS Version [e.g. 11]
+ - Zettlr Version [e.g. 0.15]
+ - Screen Resolution [only necessary if the bug is relating to the GUI]
+
+<!-- If there is anything else that might be of interest, please provide it here -->
+## Additional information