implement non-EXE support

[elijah-wright]

this PR adds non-EXE support by running ShellExecute with the default application for files. I'm not familiar with AssocQueryStringW, so this should not be merged until someone who does know that function can look through it. invoking AssocQueryStringW twice, first to get buffer_size and then to fill the buffer, doesn't seem elegant

I tested this on Windows 10 with sudo support. text files appeared to work, but any other file did not, likely due to some strange behavior with programs in locations with a space as defined in shell/open/command. it may work on Windows 11, I have a machine I can test this on, but until that's fixed this shouldn't be merged