More Readable Tests, Docs, ... [this is a draft]

I used [axios] in a project and while I was reading the docs to learn how multiple interceptors work, I had to dig all the way into the tests and into the source code to finally understand it fully.

This led me to improve the tests to document how axios handles multiple interceptors (as they call them). I refactored the tests and added some, that imho make it more explicit how it works. See my branch here.

In order to update the docs, which was my initial goal, I used test-stitcher, to pull out the descriptions and massage them a little bit so they fit well into the docs.