Update issue templates

Add issue template for kaniko bugs. Should fix #338

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,23 @@
+---
+name: Bug report
+about: Report a bug in kaniko
+
+---
+
+**Actual behavior**
+A clear and concise description of what the bug is.
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. ...
+2. ...
+
+**Additional Information**
+ - Dockerfile 
+   Please provide either the Dockerfile you're trying to build or one that can reproduce this error.
+ - Build Context
+   Please provide or clearly describe any files needed to build the Dockerfile (ADD/COPY commands)
+ - Kaniko Image (fully qualified with digest)