Pentatonic and other non-heptatonic scales (and their modes)

[XBagon]

I feel like, when wanting to add more complex scales and modes, a small rework of ScaleType and Mode has to be done.
Both are targeted at 7-tone scales and I guess it would need enums for mode and scale for each n-tone scale. Or maybe I'm missing some music-theoretical concept.
I'm willing to add these features, but might need a bit more direction.

[ozankasikci]

I believe there are more important issues than implementing more complex scale types atm. Please check the Roadmap in the README, i would love to get some help with finishing up the implementation of minor scales instead, which is the first bullet point in the Roadmap.