new plugin colour grading for gimp 3

[rich2005]

Just seen your update. I did find it a bit flaky: Win11 / Gimp 3.2.4 Worked once then did not work. I did get a "seems to work each time" when I made a C:\gimp-plugins\ folder and added that to the plug-ins paths and put the plugin there.

However, MrQ has a mod here: https://discuss.pixls.us/t/colour-gradin...2/57335/14 that going by the comments, helps.