Build doc.rs with unstable enabled (#326)

Author: skmcgrail

aws-lc-rs/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "aws-lc-rs"
 authors = ["AWS-LibCrypto"]
-version = "1.6.0"
+version = "1.6.1"
 edition = "2021"
 rust-version = "1.60"
 keywords = ["crypto", "cryptography", "security"]
@@ -24,6 +24,7 @@ exclude = [
 
 [package.metadata.docs.rs]
 rustdoc-args = ["--cfg", "docsrs"]
+features = ["unstable"]
 
 [features]
 alloc = []