Refactor of entire project

[thomas-lowry]

I've been working on refactoring this project.

Here are a summary of improvements:

General improvements

• refactored entire project with a rollup build configuration
• added package.json
• added prettier
• moved JS to ES6 modules over IIFE
• removed iconInput.js (Figma no longer highlights icons on focus on inputs)
• replaced SCSS vars with CSS vars to share variable/base with Figma Plugin DS Svelte
• introducing new base also adds a selection of utility classes for flex / spacing
• improvements to switch, checkboxes and radio buttons

Select menu improvements

• added disabled states
• automatically reinitialize menu when menu items are modified
• expanded drop down will scroll and ensure menu fits within plugin iFrame
• icon ability to include an icon within input

[thomas-lowry]

Closing this as I have abandon Rollup in favor of Gulp; greatly simplifies things and better plugin ecosystem as far as inline sources is concerned.