Add schnorr signature and tests for bip 340

[guha-rahul]

addresses #274

[MSghais]

We need a function to sign Nostr event like the Struct below, or how convert a Struct Nostr Event as a felt or ByteArray, it's the main used Struct in our repo and to sign Nostr Social event, we need this struct:

    let request = SocialRequest {
        public_key: recipient_public_key,
        created_at: 1716285235_u64,
        kind: 1_u16,
        tags: "[]",
        content: claim,
        sig: Signature {
            r: 0xf1dac3f8d0d19767805ca85933bdf0e744594aeee04058eedaa29e26de087be9_u256,
            s: 0x144c4636083c7d0e3b8186c8c0bc6fa38bd9c6a629ec6e2ce5e437797a6e911c_u256
        }
    };

[MSghais]

We need also a conversion between this two types of Signature, like present in the others bip340 implement in our repo, and used in Nostr event:

sig: Signature {
r: 0xf1dac3f8d0d19767805ca85933bdf0e744594aeee04058eedaa29e26de087be9_u256,
s: 0x144c4636083c7d0e3b8186c8c0bc6fa38bd9c6a629ec6e2ce5e437797a6e911c_u256
}

[MSghais]

lfg! Let's change after the ODHack:

• Sign with ByteArray to sign Nostr event deseriliazed
• Add the VRF for the generate private key

@guha-rahul