Transcript crate with both a merlin backend and a basic label len value backend

Moves binding factor/seeded RNGs over to the transcripts.

crypto/transcript/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "transcript"
+version = "0.1.0"
+description = "A simple transcript definition"
+license = "MIT"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+edition = "2021"
+
+[dependencies]
+rand_core = "0.6"
+rand_chacha = "0.3"
+
+digest = "0.10"
+
+merlin = { version = "3", optional = true }
+
+[features]
+merlin = ["dep:merlin"]