Add a template for pull requests (#15)

Author: ctypeh

.github/pull_request_template.md

@@ -0,0 +1,13 @@
+## Overview
+
+<!--Please summarize your changes and provide context for them!-->
+
+-
+
+## Demonstration
+
+<!--If your PR has any visual changes, please include screenshots or a short video.
+In Safari, you can right click a page, choose "Save Page As" and select PNG format.
+As a simple way to capture the entire state of the page after your changes.-->
+
+<!--If your PR does not have any visual changes, please describe how it can be verified.-->