Start a new submission

[jasnakai]

Covered in this PR

This PR implements the start a new submission functionality described in GSA-TTS/FAC#424.

Allows user to start a new audit submission.

Preview

Acceptance Criteria:

• Should see "start a new submission" header, the terms checkbox unchecked and the "start a new submission" button greyed out.
• When I check the checkbox, the "start a new submission" button should be active. When I click it, I should be on the "Submission criteria check" page.
• When I click the "terms and conditions" link, I should see the "Accept and start a new submission" in modal, I should be able to dismiss the modal or continue to the "Submission criteria check" page.

Test Case Criteria:

• Modals are hidden by default.
• "Start a new submission" button is disabled by default.
• Checking the checkbox enables the "Start a new submission" button.
• Clicking the "Start a new submission" button takes user to the first step of a new audit submission.
• Displays the terms and conditions modal when "terms and conditions" link is clicked.
• Can click the "Accept and start a new submission" button to navigate to the first step of a new audit submission.
• Can closes modal by clicking close button or "Go back" button or clicking on modal overlay.

Not covered in this PR

• Data table functionality.

[heymatthenry]

@jasnakai I should've mentioned this on your PR that created this page, but be sure to add the url for the page to the pa11y configs and to the a11y lighthouse cypress spec.