Add a Pull Request template

[tlentali]

It would be nice to have a Pull Request template to improve the documentation of the change in the project.

By adding a template to .github/PULL_REQUEST_TEMPLATE/pull_request_template.md, it should work. Fill it with :

## Describe your changes

## Issue ticket number and link

## Checklist before requesting a review
- [ ] I have performed a self-review of my code
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics?
- [ ] Will this be part of a product update? If yes, please write one phrase about this update.

This is not mandatory, but nice to have to enhance community standard on the project.