[FEATURE]: Support loading SpectralDistribution from IES TM-25 ray files

[gsuberland]

Description

IES TM-25 ray files are commonly provided by lighting manufacturers as a way of documenting the spatial characteristics of their products. These files also contain spectral tables that contain one or more SPDs for the emitter. Often manufacturers do not publish machine-readable spectral information, e.g. only publishing a graph in a datasheet, so a ray file can be very useful in that scenario.

It would be very helpful if this library had a helper function that could extract each spectral table from a TM-25 ray file as a SpectralDistribution object. The spectral table format within the file is simply a 32-bit integer specifying the number of pairs in the table, followed by an array of IEEE754 single-precision floating point number pairs, the first being the wavelength and the second being the relative weight. This table comes immediately after the file header block, flags block, and description header block, all of which are simple to parse, so complete parsing of the TM-25 format is not required.

The official IES TM-25-20 standard is paywalled, but there are existing open source implementations that should be easy to reference:

• https://github.com/LarryBoxler/IESTM25RayFiles/
• https://github.com/JuliusMuschaweck/TM25RaySetTools

I have personally used that first library for extraction of SPD information from ray files, but it's far less convenient than being able to do it directly in Colour.

If access to the standard is required for this feature, I'd be willing to sponsor the purchase.