Add github-binarycache option to use built in cache #70

Job	Run time
test-vcpkg-action (ubuntu-20.04, x64-linux-release, false)	26s
test-manifest (ubuntu-20.04, x64-linux-release, false)	24s
test-vcpkg-action (macos-11, x64-osx-release, false)	1m 16s
test-vcpkg-action-latest-vcpkg-release (ubuntu-20.04, x64-linux-release, false)	28s
test-manifest (macos-11, x64-osx-release, false)	9s
test-vcpkg-action (windows-2019, x64-windows-release, false)	10s
test-vcpkg-action-latest-vcpkg-release (macos-11, x64-osx-release, false)	1s
test-manifest (windows-2019, x64-windows-release, false)	12s
test-vcpkg-action (ubuntu-20.04, x64-linux-release, true)	8s
test-vcpkg-action-latest-vcpkg-release (windows-2019, x64-windows-release, false)	11s
test-manifest (ubuntu-20.04, x64-linux-release, true)	8s
test-vcpkg-action (macos-11, x64-osx-release, true)	7s
test-manifest (macos-11, x64-osx-release, true)	9s
test-vcpkg-action (windows-2019, x64-windows-release, true)	9s
test-vcpkg-action-latest-vcpkg-release (ubuntu-20.04, x64-linux-release, true)	11s
test-manifest (windows-2019, x64-windows-release, true)	13s
test-vcpkg-action-latest-vcpkg-release (macos-11, x64-osx-release, true)	1s
test-vcpkg-action-latest-vcpkg-release (windows-2019, x64-windows-release, true)	16s
	4m 39s

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