[Wallet] add SigmaJS prover

[arobsn]

It must fully implement ISigmaProver interface

fleet/packages/wallet/src/prover/prover.ts

Lines 34 to 38 in d7eee65

	export interface ISigmaProver {
	signTransaction(unsignedTx: UnsignedTransaction, keys: ErgoHDKey[]): SignedTransaction;
	signMessage(message: ErgoMessage, key: ErgoHDKey): Uint8Array;
	verify(message: Message, proof: Uint8Array, publicKey: ErgoHDKey | Uint8Array): boolean;
	}

[shubham5080]

does this issue need to work on ?