USWDS-Proposals: Create Prefill pattern proposal

[jaclinec]

We have finished the UX and accessibility evaluation (#400) of the prefill pattern proposed by the VA and are moving forward. Now we need to create a formal proposal.

Using the information gathered in the prefill proposal initial UX/a11y evaluation as well as the draft webpage of the new prefill pattern, fill out the proposal template with the prefill pattern information.

[cfpollack]

@jaclinec here is a Draft of formal pattern proposal for you to review. Thanks!

[jaclinec]

I finished reviewing the draft and left some comments. Mostly just need to add some screenshots/demos from the VA's proposal and there are a couple of outstanding comments that need input from Feds.

@cfpollack once you add the screenshots, this should be ready for federal review. I'd send to Anne and Amy Cole first for initial review. Once their input is incorporated, it can be sent to FFR (fed final review). Thank you!

[cfpollack]

Hi @annepetersen and @amycole501 Please find the Prefill pattern proposal ready for your initial review. Thanks!