Use shinymeta to capture logic in apps and to expose it as code.

In order to improve the user experience here are some feature request for this section :

• change title of the tab to : "2 - Energy Calibration"
• replace the overall disposition by something like the attached file
  requestion git.pdf

Describe the solution you'd like
It would be nice to add some channel-energy reference by default in the energy preset of the settings tab.

Default values could be :

83 238.63
478 1460.82
856 2614.51

When selecting the "baseline corrected" plot option, and clicking the "export data" button, the exported data are the one of the "raw spectrum".
This does not allow the "baseline corrected" curve to be exported in another dataViz software. As the interface is designed, it is expected that two types of data sets can be downloaded.

Add a button in the import module to remove all imported spectra.

It would be helpful to add a "Help" tab (before the about one) that allows us to read the documentation of the package (a least), and a specific guide for the shiny version (at best).

Chanel-energy pairs preset is not updated when selecting a new spectrum in the energy scale calibration tab.

Describe the bug
Energy calibration tab say Error : impossible de trouver la fonction slice_signal while Console return the following warning : Error in slice_signal: impossible de trouver la fonction "slice_signal" [No stack trace available]

To Reproduce
Load any spectrum in import tab and click on calibration tab.

Additional context
In Gamma package, slice_signal function does not exist and has been replaced by signal_slice.