added back audio volume control, was removed in https://github.com/phetsims/vibe/commit/3bf8488a8801605887d34506255cfb862cc07f77#diff-c7c6005c8d6af665ee7c3b46c2c37a7a, see https://github.com/phetsims/vibe/issues/36
added back audio volume control, was removed in https://github.com/phetsims/vibe/commit/3bf8488a8801605887d34506255cfb862cc07f77#diff-c7c6005c8d6af665ee7c3b46c2c37a7a, see https://github.com/phetsims/vibe/issues/36

phetsims/vibe,phetsims/vibe,phetsims/vibe