Changes PR template, removed checkboxes and added new points (#1118)

* changes PR template, removed checkboxes and added new points

* added: link issues

* Update pull_request_template.md

* Update pull_request_template.md

* Update pull_request_template.md

* added acceptance criteria for maintainers

* fixed typo

* + maintainers link github issues

Co-authored-by: Matthias Urhahn <darken@darken.eu>