Add instructions on how to run the tests to the documentation pages

[santisoler]

I open this issue to keep track of the addition of instructions on how to run the tests into the documentation pages.

See #10 for reference.

Note

This Issue was opened as part of the JOSS review process: openjournals/joss-reviews#7021

[santisoler]

@sinanozaydin started adding instructions on how to run the tests in 75a759d.

I think these are enough to meet JOSS requirements for publication. I'll leave this issue open in case the authors want to keep working on it.

Feel free to close it if you desire.