Is your feature request related to a problem? Please describe.
No, The idea is to add the support that if you add a texture ending in _e, it will be converted into a emissive texture, working like this with optifine or other mods with shaders

Describe the solution you'd like
I don't know how difficult it is, but adding support for textures ending in _e or adding emissive textures is as simple as adding the new texture along with the rest of the mob textures carpet

Describe alternatives you've considered
If this cannot be done in the base mod or it is complicated, you can create an extra datapack or mod that can perform this function

Additional context
This is more than anything a change to make adding emissive textures easier for people who don't know how to create or modify xml files.