factor out getGameLevelsSchema, use in equality-explorer and fourier-making-waves, https://github.com/phetsims/query-string-machine/issues/47
factor out getGameLevelsSchema, use in equality-explorer and fourier-making-waves, https://github.com/phetsims/query-string-machine/issues/47

phetsims/vegas,phetsims/vegas,phetsims/vegas