ETS2 - Sound Fixes Pack V20.51 (1.38.x)

Version 20.51 Changelog:
1 new Bell 206 helicopter sound added to array.

Version 20.50:
Improved sound range for helicopter sound.

Version 20.49:
Adjusted helicopter sound distance based effects.

Version 20.48:
Updated sound for helicopter (experimental) with doppler and distance based effects.

Version 20.47:
1 additional exterior view asphalt tire sound.

Authors: * SCS Software for base sounds
* Drive Safely for sound edits, some sound samples, and for compiling mod
* antonvezdehod for high speed tire sound
* Deltatristar500 for an external parking brake sound sample
* Grinch for default railroad crossing bell sound rework
* kriechbaum for light switch sound
* Vasily EVR for some air brake sound samples