Finally took some time to bootstrap unit tests for the frontend part of Software Heritage
web applications.

Those tests are compiled with webpack and executed by node.js in a Javascript emulated headless
DOM environment (jsdom) through the use of the mocha tests runner.

First implemented tests are about source code highlighting features.

To run the tests, execute the following commands in the root folder of swh-web:

$ yarn install
$ yarn test

This is still a work in progress.

Related T1769