Added general developer readme to check-in root. (#21281)
Added general developer readme to check-in root. (#21281)

* Added general developer readme to check-in root.

* Fixed typos and added details.

* Suggested changes from review.

* Update src/applications/check-in/README.md

Co-authored-by: Adrian Rollett <01e9f763872cf66da3f2a6b9ddd94c5029accd6d@gmail.com>

* Apply suggestions from code review

Co-authored-by: Adrian Rollett <01e9f763872cf66da3f2a6b9ddd94c5029accd6d@gmail.com>

* Added screenshot size specifics and UUID section.

* Force CI re-run

* Force CI re-run

Co-authored-by: Adrian Rollett <01e9f763872cf66da3f2a6b9ddd94c5029accd6d@gmail.com>
Co-authored-by: Darius Dzien <b4e0089b4cc66712379c6f61f03a8ae4c7f3f8e6@adhocteam.us>
department-of-veterans-affairs/vets-website,department-of-veterans-affairs/vets-website