Add an example in the `Readme` and improve plot.

* Add a use case with data from the 2022 field trip in the `examples` directory.
The file has 3 columns separated by a comma.
* Add the description of the file and how to invert the data in the `Readme.md`
  file.
* Changed the way distances are displayed in the plot and the the value  of the
  position of the dyke returned after the inversion.
  Before, `pos` returned the relative position of the dyke with respect to the
  position of the maximum anomaly.
  Now everything is turned back to the distances indicated in the input file
  (distances set by the users).