refactor: redesign submit page

[iuioiua]

Hash: I feel like this is missing something, but I don't know what. Any ideas, or do you think it's good?
Andy: I included minimal copy, which looks sufficient to me.

Before:

After:

[hashrock]

let me do some tweaks. please feel free to revert some changes you don't want.

• Limited content width. If white space is conspicuous, it may look better if max-width is specified.
• Wider margins throughout.
• Added labels to text fields. For accessibility, placeholder attributes should not be used in place of labels.
• It looked a little odd that the text in the button was left aligned, so I centered it.

Preview:

[iuioiua]

Looks amazing! Thanks @hashrock!