Add meson
Meson <0.51.0 doesn't support building libraries with Cargo due to custom_target only producing executables.
Cargo is needed to unlock access to packages from crates.io, which would greatly help clean up squeekboard.
There might be a different way to hack meson to work with cargo, but out of the two possible hacks, I think adding a package is the easier one (and it will undo itself on its own).
Fixes squeekboard!147 (merged)
Edited by Dorota Czaplejewicz