Add scalafmt to this template

[nicmcd]

It would be very helpful to have scalafmt integrated into this template.

[Hidden-Seed]

I used Mill to build my project, and I tried running the command mill -i __.reformat, but it didn’t seem to format any files. I’m not sure if the source files are being detected correctly.

I also set override def millSourcePath = super.millSourcePath / os.up in my build.mill Could that affect Scalafmt’s behavior?

How can I check which files are being recognized by the formatter? Any suggestions would be appreciated!