Add support for file drag 'n drop + clipboard interaction. #518

Job	Run time
Build windows-latest \|\| SHARED=OFF \|\| PLATFORM=SDL	16m 6s
Build windows-latest \|\| SHARED=OFF \|\| PLATFORM=libretro	15m 7s
Build windows-latest \|\| SHARED=ON \|\| PLATFORM=SDL	15m 24s
Build windows-latest \|\| SHARED=ON \|\| PLATFORM=libretro	14m 26s
Build ubuntu-latest \|\| SHARED=OFF \|\| PLATFORM=SDL	17m 33s
Build ubuntu-latest \|\| SHARED=OFF \|\| PLATFORM=libretro	16m 35s
Build ubuntu-latest \|\| SHARED=ON \|\| PLATFORM=SDL	17m 28s
Build ubuntu-latest \|\| SHARED=ON \|\| PLATFORM=libretro	15m 50s
	2h 8m 29s

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