Add contents of the play test plan to the Pull Request template

[stephengtuggy]

If we added the contents of the play test plan to the Pull Request template, with actual check boxes next to each, would that make it clearer what the expectation is?

that would probably be a good step; and if someone misses someone else could check it off

Originally posted by @BenjamenMeyer in #1669

[evertvorster]

That would actually be helpful to have in the template.