Feat: style and functional add feed form page 1 and 3

[Alessandro100]

closes #554
Summary:

This PR adds the conditional functionality for the Add Feed Form page 1 and 3 as well as the styling. Once this PR gets the stamp of approval from @emmambd a follow up ticket for translations and unit tests will be made

Expected behavior:

Conditional functionality

Page 1

• If official producer, there should be a third element in the stepper
• If gtfs_rt then there should be no feeds link or old feeds link
• If gtfs and updating link, old feed link required

Page 3

• If asking for interview, contact email required

Testing tips:

Go to /contribute and play around with the add feed form page 1 and 3 in particular

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with ./scripts/api-tests.sh to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)
  
  
  
  
  
  

[github-actions]

Preview Firebase Hosting URL: https://mobility-feeds-dev--pr-722-x9wpfuec.web.app

[emmambd]

Looks like there's some stray text on the Add or Update Feed page before login:

I also realized that the "Is authentication required" question should be a part of the first page if "GTFS Schedule is checked", since it affects form validation as defined in the Page 2 requirements of #554

The update feed question looks like it's still on Page 1 for realtime.

[emmambd]

LGTM!

[qcdyx]

LGTM