Save Focal Gain LUT into a data file (json, csv, etc.) to make the source code file shorter.

[peterhollender]

Totally optional but consider saving the lookup table into a data file (json, csv, etc.) to make the source code file shorter.

If you chose to do that:

• you would read the file here using importlib.resources to locate it
• you would ensure it's bundled int he install by adding it to the [tool.setuptools.package-data] section. in case hatchling doesn't bnundle it automatically

Originally posted by @ebrahimebrahim in #443 (comment)