Update PR template to more closely match version used for other projects

Update the checklist in the PR template to align better with other
Tekton Projects, in particular clarifying who is responsible for
completing the checklist.

In future we may also adopt the 'Release notes' section and leverage
this in release automation to augment the current release notes.

.github/pull_request_template.md

@@ -7,12 +7,13 @@ your descriptive commit message(s)! -->
 
 # Submitter Checklist
 
-These are the criteria that every PR should meet, please check them off as you
-review them:
+As the author of this PR, please check off the items in this checklist:
 
-- [ ] Includes [tests](https://github.com/tektoncd/community/blob/main/standards.md#principles) (if functionality changed/added)
-- [ ] Includes [docs](https://github.com/tektoncd/community/blob/main/standards.md#principles) (if user facing)
-- [ ] Commit messages follow [commit message best practices](https://github.com/tektoncd/community/blob/main/standards.md#commit-messages)
+- [ ] [Docs](https://github.com/tektoncd/community/blob/main/standards.md#docs) included if any changes are user facing
+- [ ] [Tests](https://github.com/tektoncd/community/blob/main/standards.md#tests) included if any functionality added or changed
+- [ ] Follows the [commit message standard](https://github.com/tektoncd/community/blob/main/standards.md#commits)
+- [ ] Meets the [Tekton contributor standards](https://github.com/tektoncd/community/blob/main/standards.md) (including
+  functionality, content, code)
 
 _See [the contribution guide](https://github.com/tektoncd/dashboard/blob/main/CONTRIBUTING.md)
 for more details._