Describe the suggestion
On startup, search config folder RPs for lang files and concatenate their contents. Move the contents into a lang file in an "ImmersiveRailroading" resource pack located in the resource pack directory. IR RP would be auto-assigned an mcmeta version number based on the MC for the installed UMC.

Applications of the suggestion
Lang files are not loaded if the resource pack is loaded via the config folder method. They must be loaded via the resource pack menu to work properly.

I don't thing there's a good way to do this unfortunately