Define a template for PRs and issues

[Krusty93]

As user or developer, I'd like to have a template when I open a new issue or a new PR

Related docs:

• https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository
• https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/creating-a-pull-request-template-for-your-repository