Update MacOs compatibility to use more recent FUSE extension

[nschoellhorn]

The cask osxfuse is still on version 3.x of the library. This is pretty outdated, since there's already a 4.0.5. I updated the README to use another cask called macfuse which corresponds to the newer version of osxfuse. It seems that while moving up in versions, they also changed the library package name to "fuse" as on other platforms, instead of the previous "osxfuse". Hence, I also updated the build.rs file to be able to build on the newer version.

Instead of just changing the name, we could also implement a check for both names: osxfuse and fuse when building on MacOS. I am happy to adapt this PR if you want.
With this new library version, the crate builds perfectly fine on the new Apple Silicon MacBooks 👍

[Minoru]

JFYI this crate is barely maintained. There is a more actively maintained fork, https://github.com/cberner/fuser, which seem to already have the changes you propose here.