Add ability to create custom wavelength params

[Cédric Champeau]

Currently the known spectral rays are hardcoded as an enum:

astro4j/jsolex-core/src/main/java/me/champeau/a4j/jsolex/processing/params/SpectralRay.java

Lines 29 to 34 in 56c1dac

 H_ALPHA("H-alpha", KnownCurves.H_ALPHA, 0.25d, 656.281d), 
 H_BETA("H-beta", null, 0.25d, 486.134), 
 CALCIUM_K("Calcium (K)", KnownCurves.CALCIUM, 0.7d, 393.366), 
 CALCIUM_H("Calcium (H)", KnownCurves.CALCIUM, 0.7d, 396.847), 
 SODIUM_D1("Sodium (D1)", null, 0.25d, 589.592), 
 SODIUM_D2("Sodium (D2)", null, 0.25d, 588.995), 

A user has expressed interest in adding their own wavelengths. We should evaluate how to do this, in particular in such a way it is compatible with the CLI version.

[Artimon]

Thanks Cédric!