Add support for the .SID format

[Wohlstand]

It's another popular chiptune format that we can also support, it's for the Commodore 64 platform.

The first suggested library https://github.com/libsidplayfp/libsidplayfp (Licensed under GPLv2+). If there are others with a better emulation and more permissive license, you can note me about them too.

[system64MC]

I found the cSID SID player https://github.com/mlund/csid which uses the WTF licence. Sadly, the emulation is less good than libSidPlayFP (which uses ReSID emulation core), but I think it's still okay. Didn't tried yet though. I will try it once I'm at home.

[Wohlstand]

About the libsidplayfp, some months ago I tested some tricky files given by some buddy, and I accidentally found they were played very accurate compare to another implementation which plays them brokenly

[Wohlstand]

P.S. Off topic: Links has next format:

[any text](url)

And if you just past the link itself, no need to format it, just is fine to put the link in as-is without special format

[system64MC]

Thanks for the advice, sadly, ReSID is the most accurate SID emulator. I don't know any alternatives that are as accurate as ReSID

[freq-mod]

ReSIDfp - easily the most accurate, but easily the most CPU intensive