Add the ed25519 curve (#121)

* add ed25519 curve

* changelog

* curve info

* fix

* cleanup the script

* Update ed25519/src/curves/mod.rs

* Update ed25519/src/curves/mod.rs

Co-authored-by: onewayfunc <onewayfunc@gmail.com>

ed25519/src/fields/fr.rs

@@ -0,0 +1,7 @@
+use ark_ff::fields::{Fp256, MontBackend, MontConfig};
+
+#[derive(MontConfig)]
+#[modulus = "7237005577332262213973186563042994240857116359379907606001950938285454250989"]
+#[generator = "2"]
+pub struct FrConfig;
+pub type Fr = Fp256<MontBackend<FrConfig, 4>>;