Add continuous delivery to crates.io

• https://crates.io/crates/libvlc-sys

• https://crates.io/crates/vlc-rs

• https://doc.rust-lang.org/cargo/commands/cargo-publish.html

Already added a secret deploy token CARGO_PUBLISH to Gitlab.

Should add a script which contains: cargo publish --token "$CARGO_PUBLISH"

Should only run on tagged commits, successful builds and master. And versioning?