Create PR template

[JosiahParry]

There are some common things that should be capture in a PR Template check list to reduce overhead and burden (guilty!!!).

Some of these are:

• [ ] checking the lintr using styler::style_package()
• [ ] update package down if adding a new function
• [ ] new functions should have a @returns and @example for CRAN compliance
• [ ] changes should be in NEWS.md
• [ ] add to README if appropriate