PR template

[JakobJingleheimer]

Let's add a PR template that includes a warning ([!CAUTION]) about force-pushing.

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

[AugustinMauroy]

-1 for the [!CAUTION] because pr template is filled by the author in markdown so this strange syntax will not help the author to be careful.
On contributing.md that can make sense.

So IMO having pr template + updateing contribution guidelines to include force push thing

[JakobJingleheimer]

Ahh, sure :) A big note

**************************
*                        *
* 🛑 Do NOT force-push 🛑 *
*                        *
**************************

[AugustinMauroy]

approve !