Add form labels to aid readability

[rrhyne]

The inputs on comby.live utilize placeholders for labels. When the form is filled out, the placeholder is hidden, which obscures the form input's purpose.

This is an issue for users who are being introduced to comby.live by a link to replaced code, as they will have not seen the inputs empty and have not yet learned what they are for.

Adding labels above the inputs would improve this experience.

Here's a quick design of how this would look:

Figma:
https://www.figma.com/file/2jFDywp4x0jtL3ZL1j3t0w/Comby-live-UX?node-id=0%3A1&viewport=727%2C534%2C1.0854430198669434