Update PR template to be more prescriptive

[brandtkeller]

Describe what should be investigated or refactored

It is too easy to get into a habit of checking boxes - but also the content of each box should be made more verbose. This issue is proposing the update of the template to accomplish the following:

• Checkboxes should be made singular in purpose (IE test / docs/ adr etc should be individual boxes)
• Checkboxes should only apply to tasks (remove checkbox from "type" of PR)
• Additional Verbosity for clarity?