ETS2 - Rework Vanilla Sounds V1.0

Initial project to expand the vanilla sound from Amtrucks & Eurotrucks.

Sounds already improved/or added:
-ISX15/X15 Stock.
-CAT C15.
-Paccar MX-13.
-Volvo D13

Plans for the next updates are:
-Add Navistar engine.
-Add Detroit DD13-15 engine.

Authors: Miky