Add detailed tutorial and tutorial into page

[tobiasdiez]

Similar to https://storybook.js.org/tutorials/intro-to-storybook/. Into page should outline what the tutorial covers and a table of contents.

The storybook tutorial is also very good, really takes one from nothing to a working solution.

[koppor]

This refs https://github.com/JabRef/manuals.jabref.org/issues/2 (because it is kind of a quick start)