add NV12, NV21 to PixelFormatEnum #356

Job	Run time
build linux pkg-config	2m 0s
build vcpkg (macos-latest)	10m 5s
build vcpkg (ubuntu-latest)	7m 38s
build vcpkg (windows-latest)	14m 59s
build bundled (macos-latest)	5m 8s
build bundled (ubuntu-latest)	2m 52s
build bundled (windows-latest)	7m 7s
build bundled (--release, macos-latest)	7m 6s
build bundled (--release, ubuntu-latest)	3m 16s
build bundled (--release, windows-latest)	7m 56s
build bundled (static-link, macos-latest)	5m 29s
build bundled (static-link, ubuntu-latest)	3m 42s
build bundled (static-link, windows-latest)	8m 29s
build bundled (static-link, --release, macos-latest)	5m 26s
build bundled (static-link, --release, ubuntu-latest)	3m 28s
build bundled (static-link, --release, windows-latest)	9m 31s
	1h 44m 12s

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