Update pull request template to be more meaningful

[nivisi]

Why?

The current template doesn't bring much value. It results in us skipping the checkmarks and no one reading the PR description, although it may contain some notes about the PR and the ticket.

What to do?

To make the PR template more contextualized. We can put there the implementation details, steps to test and so on.

With this, we will make the life easier for the reviewers as they will be able to jump into the context of the task from the PR description.

I would also suggest to upload a quick video demo of what has been changed/implemented.

Examples with custom templates

• Gems project;
• Onro project.