Feature: add support to the Visual Form Builder

[glaubersilva]

Description

This PR creates the Form Extension folder with a few samples demonstrating how to extend the Visual Form builder.

To accomplish that, the following items were added:

• A sample settings page in the Form Builder;
• A sample block in the Form Builder;
• A conversion class that uses the Fields API to transform the sample block in HTML input when the Donation Form gets rendered.

Also, it adds the following new scripts to compile the form extension:

npm run dev:form-extension
npm run watch:form-extension

Affects

The Visual Form Builder

Visuals

Testing Instructions

Pull this branch and then follow these steps: https://github.com/impress-org/givewp-addon-boilerplate?tab=readme-ov-file#setup--installation

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[jonwaldstein]

@glaubersilva thanks for the updates! just some minor tweaks but this is looking good. I would love to continue expanding this with multiples service providers for different domains 😄

[glaubersilva]

@jonwaldstein Thank you! The next step is to implement some gateway samples. 🤑