Update pr-checklist.yaml to include news nudge

[seabbs]

This PR updates the PR checklist to include a nudge for updating the news file.

[github-actions[bot]]

👋 Thanks for opening this pull request! Can you please run through the following checklist before requesting review (ticking as complete or if not relevant).

• [x] Read our contribution guidelines if you have not already done so.
  • [ ] If you have altered an existing class please run the tests locally (using devtools::load_all(); devtools::test()) first setting options(testDownload=TRUE, testSource=class-name) and report your findings.
  • [ ] If you have added a new data class please run the tests locally for that class (using devtools::load_all(); devtools::test()).
  • [ ] Check your code passes our CI checks and review any style and code coverage warnings.
  • [ ] Comment with details if unable to get our CI checks to pass or unable to remove all warnings.
  • [ ] Update the news file with information on your changes (crediting yourself at the same time)

Thank you again for the contribution. If making large scale changes consider using our pre-commit hooks (see the contributing guide) to more easily comply with our guidelines.

[RichardMN]

So (embarrassed cough) I get so many of these emails that I don't pay much attention to them any more but since it seems that three (four?) of my PRs are currently at the "please update NEWS.md" stage I guess I should just be glad it isn't framed with a conditional as if user_name == richardMN ...

Good idea. I will try to update NEWS.md when necessary. (My excuses are that I have tended to want to get something approved/agreed before announcing it, and that it feels odd to be "boasting" about specific contributions. I'll get over both of these.)