Jest (internetarchive#2002)

* Eslint all JS files in the repo

There are other JS files around the repo so let's lint those
as well.

* Add unit testing via the Jest framework

From now on we'll write unit tests to strengthen our code.
I begin by writing tests for two simple files.
In the process, I discover a bug in htmlquote (which I fix!)
Code coverage is reported and lowest coverage possible is defined
in package.json. We will work towards increasing this with time
as we refactor. For now code coverage is 1%.. you have to start
somewhere!!

Fixes: internetarchive#1999

Merge pull request internetarchive#1941 from shreyansh23/issue-1889

Add top margin on return ebook button to avoid collapsing with read e…

fixing click-outside readinglog btn

Merge pull request internetarchive#1355 from internetarchive/hotfix/u…

…nbreak-redirects

fix processor: setting v2 breaks for redirects

Merge pull request internetarchive#766 from internetarchive/765/hotfi…

…x/remove-lending-stats

765/hotfix/remove lending stats

Merge pull request internetarchive#747 from internetarchive/hotfix/re…

…adinglog

setting 0 default count when readinglog not present in db

Merge pull request internetarchive#726 from internetarchive/724/featu…

…re/reading-log-analytics

adding basic stats UI for reading log feature

Merge pull request internetarchive#583 from internetarchive/feature/l…

…ikes

Reading Log Feature

Merge pull request internetarchive#666 from internetarchive/refactor/…

…mobile-home2

Refactor/mobile home2

more thrillers performance tuning + tests