docs: add pull request template

Author: mishamyrt

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+<!-- Enter a brief description/summary of your PR here. What character(s) are you changing/creating and how was it tested (even manually, if necessary)? Did you hint the entire font or only the modified character(s)? -->
+## Summary of the Pull Request
+
+<!-- Other than the issue solved, is this relevant to any other issues/existing PRs? -->
+## References
+
+<!-- Please review the items on the PR checklist before submitting-->
+## PR Checklist
+* [ ] Closes #xxx
+* [ ] Requires CHANGELOG.md to be updated
+* [ ] Requires [/images/](/mishamyrt/Lilex/images/) to be updated
+
+<!-- Provide a more detailed description of the PR, other things fixed or any additional comments/features here -->
+## Detailed Description of the Pull Request / Additional comments
+
+<!-- Provide images of the character(s) that are being modified/created at different screen sizes. Clearly identifying specific code points is heavily recommended. -->
+## Before (if applicable) and After Images of the Character(s)