added decodeInvoice util

[Egge21M]

Fixes: #94

Description

Added a decodeInvoice utility function that takes in a bolt11 invoice and returns an object of type InvoiceData

type InvoiceData = {
	paymentRequest: string;
	amountInSats: number;
	amountInMSats: number;
	timestamp: number;
	paymentHash: string;
	memo: string;
	expiry: number;
};

Changes

• Added type InvoiceData
• Added decodeInvoice to utils.ts
• Added test

PR Tasks

• Open PR
• run npm run test --> no failing unit tests
• run npm run format

[gandlafbtc]

nice! We could add an import and export for this function in index.ts so it is easily accessible when importing the lib