Add PR templates

[nickfloyd]

This PR adds our standardized PR templates.

[octokitbot]

:tada: This PR is included in version 18.1.0 :tada:

The release is available on:

• GitHub release
• npm package (@latest dist-tag)
• npm package (@latest dist-tag)
• npm package (@latest dist-tag)
• npm package (@latest dist-tag)
• npm package (@latest dist-tag)
• npm package (@latest dist-tag)
• npm package (@latest dist-tag)

Your semantic-release bot :package::rocket: