Create issue template

This template will load any time a new issue is created to ensure some basic information is provided about the issue.

docs/issue_template.md

@@ -0,0 +1,19 @@
+### Is this a feature request or a bug?
+
+
+### What is the current behavior?
+<!--
+* If this is a bug, please include the steps to take to
+  reproduce the issue including any urls, screenshots, etc.
+  as helpful.
+-->
+
+
+### What is the expected or desired behavior?
+
+
+### Version information (for bug reports)
+
+* **Firefox version**:
+* **Your OS and version**:
+* **Price Tracker extension version**: