Add issue template (#976)

* Create issue template

* Refined issue template

Following suggestions by ixjlyons

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,44 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+<!-- In the following, please describe your issue in detail! -->
+<!-- If some of the sections do not apply, just remove them. -->
+
+### Short description
+<!-- This should summarize the issue. -->
+
+### Code to reproduce
+<!-- Please provide a minimal working example that reproduces the issue in the code block below.
+     Ideally, this should be a full example someone else could run without additional setup. -->
+```python
+import pyqtgraph as pg
+import numpy as np
+```
+
+### Expected behavior
+<!-- What should happen? -->
+
+### Real behavior
+<!-- What happens? -->
+
+```
+An error occurred?
+Post the full traceback inside these 'code fences'!
+```
+
+### Tested environment(s)
+
+ * PyQtGraph version: <!-- output of pyqtgraph.__version__ -->
+ * Qt Python binding: <!-- output of pyqtgraph.Qt.VERSION_INFO -->
+ * Python version: 
+ * NumPy version: <!-- output of numpy.__version__ -->
+ * Operating system: 
+ * Installation method: <!-- e.g. pip, conda, system packages, ... -->
+
+### Additional context