Option for a trichromat passthrough method?

I'm interested in setting up my build script with a method of `trichromat` (and with all the other methods in place but commented out, perhaps) that just returns the styles completely unchanged. That would allow me to make a single-line configuration change or use an environment variable to quickly check out the results - ideally without having to look up the spelling.

I was going to fork it and add the option, but I thought I'd check first to see if you were interested in adding the feature and/or if you had opinions on the method name.

Start by locating the plugin's existing colorblind method options and the build-script configuration that selects them. Add a trichromat passthrough option whose output remains unchanged, then verify that it can be selected through the documented configuration path and produces unchanged styles.

Written by the indexing model from the issue text.