Installed VorbisConfig.cmake needs Ogg dependency

[madebr]

An installed VorbisConfig.cmake needs Ogg

vorbis/cmake/VorbisConfig.cmake.in

Lines 4 to 6 in 84c0236

	if(NOT TARGET Ogg::ogg)
	find_dependency(Ogg REQUIRED)
	endif()

This assumes ogg is installed with cmake and OggConfig.cmake/FindOgg.cmake is somehow available.

Vorbis itself ships a FindOgg.cmake module and thus does not require ogg to provide OggConfig.cmake.

So I propose to installFindOgg.cmake as well, and add it to CMAKE_MODULE_PATH inside VorbisConfig.cmake.

I do something similar in SDL_mixer to find the various dependencies.
(SDL_mixer only needs the dependencies when building a static library)