Add Contributing to Amazon Cloud Player script

[jiri-janousek]

• Author: Jiří Janoušek janousek.jiri@gmail.com
• Reviewed by: FIXME

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[jiri-janousek]

Hello @SteVwonder . If you agree with proposed changed, but don't have time to merge them, let me know and I'll merge the branch by myself.

[jiri-janousek]

Merged without review as the maintainer is MIA.