Introduces a **ResponsiveProvider** as the sole location that tracks
window size and makes that info available to the entire app. This can be
used for media queries and size-based component switching.
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Co-authored-by: Jed Fox <git@jedfox.com>

* mobile detection

* remove intermediate variable

* Split the Settings component into multiple files (#434)
* Remove need for isMobile in CSS: lean on media queries in styles.js and glamor

Co-authored-by: Matiss Janis Aboltins <matiss@mja.lv>
Co-authored-by: Jed Fox <git@jedfox.com>