Responsive widths

A simple plugin that saves an object structured like:

{large: "", medium: "", small: ""}

Where each key represents a screen size, and the screen size metric is stored as a string, assumed to be a percentage.

This plugin is ideal for a grid column block, rendered within a modular content field of a grid block.

Suggested implementation:

1. Add a new JSON field to a block that respresents a column
2. in the field editor > presentation tab, select "responsive widths" as the field editor
3. Create a modular content field in a block that represents a grid, only allowing blocks that contain the "responsive widths" field (i.e. grid column blocks)

You can check out the youtube video tutorial on the suggested implementation here: https://youtu.be/OgZE1A8W0hA