sodium: add licence key in Cargo.toml
This matches the spdx identifier in the source files.
@@ -4,6 +4,7 @@ version = "0.1.0"
authors = ["Jordan Petridis <jordan@centricular.com>"]
repository = "https://gitlab.freedesktop.org/gstreamer/gst-plugin-rs"
description = "libsodium-based file encryption and decryption"
+license = "MIT"
edition = "2018"
[dependencies]
