Modula-2 file extension '.def' is missing

https://github.com/github-linguist/linguist/blob/d352058f979caab69b5c0876cd4992ce43a29132/lib/linguist/languages.yml#L4222

Modula-2 separates interface and implementation in separate files.

Interfaces (historically but incorrectly called definition modules) have file extension '.def'.
Implementation and program modules have file extension '.mod'.

This is similar to C's '.h' and '.c' files but unlike C, the modules are NOT preprocessor includes, they are separate compilation units and it is entirely impossible to write Modula-2 libraries without having '.def' files. This is not a matter of choice or style, this is an absolute requirement.

Not supporting '.def' as a file extension for Modula-2 means that the entire syntax highlighting for Modula-2 is completely broken as it is 50% incomplete.

So, can you please add recognition for the '.def' file extension.

I had reported this many years ago, but apparently nothing has happened since and I can't even find the report now. It would be nice if this wasn't just swept under the carpet again. It should be rather easy to add.

Thank you in advance.