[libopnmidi] add new port

[dbarkar]

All provided patches are in upstream:
cmake-build-shared-libs-support.patch - Wohlstand/libOPNMIDI@76e4610
cmake-package-export.patch -Wohlstand/libOPNMIDI@a48f3f7
disable-wopn2hpp.patch - Wohlstand/libOPNMIDI@0a91e14
fix-build-without-sequencer.patch -Wohlstand/libOPNMIDI@2c348b3
fix-pmdwin-emulator-include.patch - Wohlstand/libOPNMIDI@81178c3

All features are additive.
There are two experimental emulators (pmdwin-emulator and gx-emulator), should they be included in default features? What's the best practice here?

• Changes comply with the maintainer guide
• The name of the port matches an existing name for this component on https://repology.org/ if possible, and/or is strongly associated with that component on search engines.
• Optional dependencies are resolved in exactly one way. For example, if the component is built with CMake, all find_package calls are REQUIRED, are satisfied by vcpkg.json's declared dependencies, or disabled with CMAKE_DISABLE_FIND_PACKAGE_Xxx
• The versioning scheme in vcpkg.json matches what upstream says.
• The license declaration in vcpkg.json matches what upstream says.
• The installed as the "copyright" file matches what upstream says.
• The source code of the component installed comes from an authoritative source.
• The generated "usage text" is accurate. See adding-usage for context.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is in the new port's versions file.
• Only one version is added to each modified port's versions file.

[jimwang118]

All feature passed with following triplets:
x86-windows
x64-windows
x64-windows-static

The usage has been tested successfully locally. 

find_package()
target_link_library()