Support building the layers module with vcpkg

[Zetelias]

Just a quick suggestion, to add a "layers" feature in the vcpkg port that builds the layers module.

[CodeJhF]

Thanks for using tgfx and for the great suggestion!
This has been implemented in commit 48cd318f760fd09204ba0cc827ae02b8ac64b80d. You can now use the layers feature in vcpkg:
vcpkg install tgfx[layers]
Feel free to reopen if you have any issues.