This improves usability of narrow screen widths, and also prepares for
further optimizations that would allow us to use the sidebar largely
as-is on mobile, instead of having to have a tab bar.

---------

Co-authored-by: Matiss Janis Aboltins <matiss@mja.lv>

Seems to build fine, will test later.

- Add a “hide decimal places” setting to visually hide the `.xx` from
currency values globally
- When hiding the fractional digits, slightly decrease character spacing
to allow more digits to show up

Ref: #327

New settings:
<img width="566" alt="Screenshot_2023-03-17 14 19 46"
src="https://user-images.githubusercontent.com/25517624/225986815-b884b93d-02f9-48b3-a73d-d27f90b678cf.png">


Before/after:
<img width="149" alt="Screenshot_2023-02-27 21 47 07"
src="https://user-images.githubusercontent.com/25517624/222916856-21ab4f03-56c6-4b24-8fc1-ac4b883138b7.png"><img
width="131" alt="Screenshot_2023-02-27 22 02 01"
src="https://user-images.githubusercontent.com/25517624/222916859-cf882ca3-6087-4994-818e-239c3374e412.png">

*  (prettier) adding trailing commas

* More commas

* 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>