I made a documentation change and noticed that the result when browsed
locally did not quite match what is seen when browsing from the web.
After some research, I found https://github.com/mkdocs/mkdocs/issues/2028
That described my situation well and suggested adding an extra
javascript script to the configuration. This worked exactly as desired
on my local machine. This accounts for the presence of extrajs.js
and mkdocs.yml in this request.
In addition to the display problem, "mkdocs build" generates the
documentation into a directory which is not ignored by git. I added
that directory to .gitignore as part of this request.
Finally, since I don't know how exactly the documentation makes it
to production, I made an insignificant change to one doc file as
a sanity check.
All code for unit tests is now under the `PhpSpreadsheet\Tests` namespace
which is autoloaded via composer mechanism. So there is no need for
`require()` anymore.
Also, tests were moved in `tests/` folder and phpunit should be executed from
the project root folder. This is to conform to the de facto standard, notably
in use in phpunit itself.