* Add coming soon extensions to the library

This implements #1074

* don’t call `onSelect` when disabled

thanks @paulkaplan!

* add speech image to coming soon extension

* Library: Centered sprites

* Close button component: large: added similar transition to add button
* Filter component: added autofocs, made full width

With jscodeshift thank God

Remove target pane button and actions

Add back putting the sound library in the ui

Refactored towards better convention for linting.

* Design pass on libraries to make sprites look more like they do in the SpriteSelector. Fixed scrolling overflow when reaching the bottom
* Started a colors variables file
* Added a light transform on sprite item hover

Related #12

* Covers parts of these issues: GUI layout panes (#69), sprite libraries (#12), import buttons (#64), menu bar (#67), and sprite info area (#53)

~ Refactored layout pane structure by removing `display: flex` from `.box`, by default. Declaring flex instead only where specifically needed. This helped fix layout quirks, and should help us avoid hard to find issues related to nested flex boxes

~ Added descriptive classnames to boxes/containers/wrappers. Moved more padding, margins + layout into these wrappers to help with component reusability.

~ Set up a spacer unit variable inside `gui.css`, to start keeping consistent padding, margins and rounded corners between panes. Used [CSS/PostCSS Modules](https://github.com/css-modules/postcss-modules-values) to avoid SCSS dependency.

~ Refactored inline styles from JSX, into CSS files. 2 reasons: a) prepping for reuse of CSS Module variables. b) Feels easier to debug complex flex layouts when all the styles are in one place vs JS/HTML/CSS syntax mixed together

~ Added menu bar into layout via new component, and sprite info header in sprite selector pane, with stubs for the labels + forms. Sprite items are correctly scrolling, while leaving the header fixed, in Chrome. Mostly working in FFx. Not working in Safari, IE yet.

~ Style pass on library modal

~ Experimenting with a few different transition styles: Logo in menu bar, sprite library items, Add buttons.