Convert to `cargo_embargo`

Bug: 302021139
Test: m libmls_rs_uniffi in local checkout
Change-Id: I4a6c562bf09b844b71b91e71ca830d38bf3e71c0
diff --git a/mls/mls-rs-crypto-boringssl/Cargo.toml b/mls/mls-rs-crypto-boringssl/Cargo.toml
new file mode 100644
index 0000000..8468df5
--- /dev/null
+++ b/mls/mls-rs-crypto-boringssl/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "mls-rs-crypto-boringssl"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+bssl-crypto = { path = "../../../../external/boringssl/src/rust/bssl-crypto" }
+mls-rs-codec = "0.5.3"
+mls-rs-core = "0.18.0"
+mls-rs-crypto-traits = "0.10.0"
+thiserror = "1.0.49"
+zeroize = { version = "1.6.0", features = ["zeroize_derive"] }
+maybe-async = "0.2.10"
+
+[target.'cfg(mls_build_async)'.dependencies]
+async-trait = "0.1.74"
+