Note to include PR in changelog

[ciarams87]

As a maintainer of NGF
I want to label my PR with a note label
So that NGF maintainers can highlight changes they make to be included as part of the changelog for release.

Acceptance:

• Create a Label for PR's that need a note in the change log
• The PR template is updated to include a note about the label for changelog inclusion.
• Update the pull request documentation to include the importance of including the label on an important PR.