Include example with real IBIS data

[ConorMacBride]

This pull requests adds a new example to the example gallery. This example uses real IBIS data, a 60 by 50 grid of spectra with 27 wavelength points. A set of labelled spectra are also included for training a neural network. A file containing the result of fitting the included spectra is also included, so the user can compare their values. The LabellingTutorial.ipynb has been updated to use the same data and run as-is.

[codecov]

Codecov Report

Merging #31 (ddda5b4) into main (0bf27e5) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #31   +/-   ##
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  Coverage   94.33%   94.33%           
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  Files          16       16           
  Lines        1217     1217           
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  Hits         1148     1148           
  Misses         69       69           

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