Create Rust Dockerfile

[Xanewok]

What does this PR do?

Attempts to add a Dockerfile with a prepared Rust environment with latest Rust stable version installed (installed using rustup toolchain manager and also bundles standard rls language server).

I hope I did everything correctly and that's needed at all (couldn't see Rust support out of box or any other mentions whatsoever), please let me know if I should do this differently.

What issues does this PR fix or reference?

None

New behavior

Create a new Rust recipe containing latest Rust stable installed, along with the rustup-shipped rls Rust language server.

Tests written?

No

Docs updated?

Not sure what to add to http://github.com/eclipse/che-docs unfortunately 😢