Add libudev-dev to Ubuntu dependencies

[Zooce]

Bevy seems to now depend on libudev-sys (and thus libudev-dev):

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: "`\"pkg-config\" \"--libs\" \"--cflags\" \"libudev\"` did not exit successfully: exit code: 1\n--- stderr\nPackage libudev was not found in the pkg-config search path.\nPerhaps you should add the directory containing `libudev.pc\'\nto the PKG_CONFIG_PATH environment variable\nNo package \'libudev\' found\n"', /home/zooce/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libudev-sys-0.1.4/build.rs:38:41
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: build failed

This PR adds libudev-dev to the Ubuntu 20.04 dependencies.

[Zooce]

#330 mentions another similar error for the alsa package, which seems to be from the alsa-sys crate, but that issue mentions libsdl2-dev. I'm just not sure what the correct dependency is.

[CastilloDel]

I also needed to install libudev-dev for libudev-sys v0.1.4 to compile. In debian bullseye/sid

[cart]

Awesome. Thanks for helping us stay up-to-date!

[DJMcNab]

@Zooce please respond in #2373 for the relicense to MIT/Apache 2.0. Thanks!

[Zooce]

Done