os/mac/pkgconfig: add pc files for Big Sur

[Bo98]

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• Have you added an explanation of what your changes do and why you'd like us to include them?
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Supplying both 10.16 and 11.0 for now. We may remove 10.16 in the future should the versions unify.

As of beta 1, the only library updated was sqlite3 from 3.28.0 to 3.31.1.

[MikeMcQuaid]

Thanks @Bo98!