housekeeping: adding PR template
housekeeping: adding PR template

Creating a template, so that the requirements for good PRs can
be codified, instead of the PR submitters warned after the PR
was already submitted.
Adding items that I know of at the moment.

Change-type: patch
Signed-off-by: Gergely Imreh <74449e3aedfaa0d6a6bf65a913316ac698c6961f@gmail.com>

resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin