Update the Cargo.toml in preparation of publishing

- Add the keys suggested for publishing
- Move the third-party crates in a separate directory
- Add a version for each crate dependency

Cargo.toml

@@ -6,6 +6,8 @@ edition = "2018"
 build = "build.rs"
 include = ["/src/**", "/Cargo.toml", "/build.rs"]
 license = "BSD-2-Clause"
+description = "The fastest and safest AV1 encoder"
+repository = "https://github.com/xiph/rav1e/"
 autobenches = false
 autobins = false
 
@@ -38,14 +40,14 @@ serde_json = { version = "1.0", optional = true }
 dav1d-sys = { version = "0.2", optional = true }
 aom-sys = { version = "0.1.2", optional = true }
 scan_fmt = { version = "0.2", optional = true }
-ivf = { path = "ivf/", optional = true }
-avformat-sys = { path = "avformat-sys/", optional = true }
+ivf = { version = "0.1", path = "ivf/", optional = true }
+avformat-sys = { version = "0.1", path = "crates/avformat-sys/", optional = true }
 rayon = "1.0"
 bincode = "1.1"
 arrayvec = "0.4.10"
 
 [build-dependencies]
-nasm-rs = { version = "0.1", path = "nasm_rs/", optional = true }
+nasm-rs = { version = "0.1", path = "crates/nasm_rs/", optional = true }
 vergen = "3"
 
 [target.'cfg(unix)'.build-dependencies]
@@ -88,4 +90,4 @@ codegen-units = 1
 lto = true
 
 [workspace]
-members = ["ivf", "nasm_rs"]
+members = ["ivf", "crates/nasm_rs", "crates/avformat-sys"]