Add GitHub PR template

Author: mykulyak

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,19 @@
+<!--
+Thank you for submitting a pull request to Fresha API tools.
+-->
+
+## Motivation and Context
+
+What problem does this PR resolve ?
+
+## Type of changes
+
+What types of changes does your code introduce? Put an `x` in all the boxes that apply:
+
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
+
+## Details
+
+More information on things that require more attention while reviewing.