Create PULL_REQUEST_TEMPLATE.md

Basic template to use when submitting pull requests.

Author: Sam Spencer

.github/PULL_REQUEST_TEMPLATE.md

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+### Summary
+*Replace this line with a short description of the content in your pull request.*
+
+### Fixes Issues
+This pull request fixes the following issues:  
+- #
+
+### Changes
+The following changes are included in this pull request:  
+- *Replace this with a description of a change*
+
+### Notes
+- [ ] This pull request makes breaking changes, and if so, involves the following:  
+  - [ ] Public API availability  
+  - [ ] Internal functionality or behavior  
+- [ ] I have run and ensured that this pull request passes all XCTests  
+
+*Include any additional notes on your pull request*