adds readability widget

[Smullz622]

Adds the readability widget developed by NC State Libraries

The only customization at this time is changing to psu brand colors.

Current fields are warm background, highlight links, open dyslexic font, and remove images. There's potential in the future to customize further by changing the fields you can toggle on/off (ex. ADHD friendly fonts, etc)

[ajkiessl]

I think we can remove widget.css and widget.css.map. Ultimately, shakapacker should compile the widget.scss into the application.css and application.css.map and throw that in the public/packs/css directory. Otherwise this looks good!

[ajkiessl]

Also, this should probably be removed in widget.scss:

/*
* to compile run this code from the root of this app
* sass --watch widget.scss:widget.css
*

Since shakapacker will handle this.

[ajkiessl]

Looks good!