Please provide better build instructions

[martinvonwittich]

While attempting to build netmuxd with cargo build, I stumbled over both #31 and #23. The current instruction:

Make sure both rusty_libimobiledevice and plist_plus are buildable.

wasn't especially useful, because the failure to build plist_plus was the first error I encountered and therefore tried to fix, but plist_plus doesn't actually provide any instructions.

The required steps to fix the build on my Ubuntu 22.04 machine were:

1. Install the libimobiledevice build dependencies as explained in cargo build has errors #23 (comment) (though I skipped libimobiledevice-glue-dev which is apparently not yet available in Ubuntu 22.04, but also not required yet)
2. Build with cargo build --bin netmuxd instead of cargo build as explained in cargo build Error：unresolved import rusb #31 (comment)