Accept karma.conf.cjs as configuration file

[DamienCassou]

Currently, karma looks for these configuration files:

• ./karma.conf.js
• ./karma.conf.coffee
• ./karma.conf.ts
• ./.config/karma.conf.js
• ./.config/karma.conf.coffee
• ./.config/karma.conf.ts

I would like to add karma.conf.cjs to this list (and maybe .config/karma.conf.cjs).

A .cjs extension makes sense in project with type: "module".

Eslint already searches for a .cjs configuration file for example.

[devoto13]

I think we should add both.

PR is welcome :)