[feature] add integration support with qmake

[xiaoyifang]

Is your feature request related to a problem? Please describe.

there are still many qmake project out there.
If qmake and vcpkg can work easily together , it will increase the usage area of vcpkg.

Proposed solution

after

vcpkg integration install

PKG_CONFIG_PATH will be set correctly.

then in qmake project.

CONFIG += link_pkgconfig
PKGCONFIG += library-name

Describe alternatives you've considered

No response

Additional context

No response