Minor improvements to the PR template (#17782)
Closes #17616
Summary of the issue:
There is inconsistent use of colons (":") after prompts in the PR template.
Description of user facing changes
The PR template now has colons following all prompts
The PR template now has a new "Developer facing changes" section
The PR template now reminds users to use "Closes"/"Fixes"/"Resolves" to link the targetted issue
The Pull Request Template Explanation and Examples document has been updated
Description of development approach
Read templates and made adjustments as necessary.
Read the template documentation, making minor fixes and documenting the new section.
