Update issue templates

Author: diehlpk

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,32 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+## Expected Behavior
+
+... Please describe the behavior you would have expected.
+
+## Actual Behavior
+
+... Please describe the behavior you actually observed.
+
+
+## Steps to Reproduce the Problem
+
+... Please be as specific as possible while describing how to reproduce your problem.
+
+  1.
+  1.
+  1.
+
+## Specifications
+
+... Please describe your environment
+
+  - HPX Version:
+  - Platform (compiler, OS):