The Studio lights are now loaded from disk. The location is
`datafiles/studiolights` they need to be JPG for now. JPG cannot store
HDRI color range but they are clamped inside the Workbench
engine for speed reason. I didn't select JP2K as it might not be
enabled.
Users can add upto 20 HDRI files. This limitation is inside the
RNA_space.c Currently the icons are calculated when you first open the
selection box for the HDRI's. We could add them to a background
rendering later.
I added 2 test files a sky texture rendered in Cycles and an HDRI from
cloud.blender.org.
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