Mode master volume

[t3knomanzer]

Issues

• Fixes Master volume mode #40
• Resolves #
• Closes #

Description

Added support to control master volume.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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• Compiled and tested requested changes
• Updated the documentation, if necessary
• Updated the LICENSES file, if necessary
• Reviewed the guidelines for contributing to this repository
• Requesting to pull a topic/feature/bugfix branch

Further comments

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