AMP4Email Forms- Signature/FreeDraw Pad

### Description

Our usecase is inviting email recipients to sign our petition forms directly in the email without leaving the page. AMP4Email forms is a great solution for us, but the issue a significant number of our petitions legally require a handdrawn signature.

### Alternatives Considered

We're considering directly using appsheet in an iframe in the email since google appsheet has a native signature pad, but still working this option out

### Additional Context

_No response_

Start by reading the AMP4Email forms documentation and implementation; the issue does not name a file, test, or entry point. Investigate whether a hand-drawn signature pad can work within an email without leaving the page, and define completion as a usable signature capture flow for legally required petition forms.

Written by the indexing model from the issue text.