Emulated and ed25519 crates

[avras]

Adding two crates

• bellpepper-emulated is a crate for implementing non-native arithmetic. It is inspired by the inspired by the emulated package in Gnark. It has been tested via an implementation of ed25519 curve operations. Further testing through implementation of other curves like secp256k1 is a TODO.
• bellpepper-ed25519 is a crate for implementing ed25519 curve operations. It does NOT support ed25519 signature verification as of now. Only point addition and scalar multiplication are implemented.

[avras]

I am fixing the cargo clippy warnings. Will commit the changes soon.