Potentially breaking fix

Patch includes:

1. README edits
2. New argument check for node-driver hash function.

Point 2 enforces not using strings in nodejs environments without type-checking (e.g. SW contracts).

Meaning: don’t allow string as data argument for hash(data: Uint8Array, algorithm?: string): Promise<Uint8Array>;

This ensures both code portability for browser execution, and future proofing against arweave-js upgrading to use NodeJS Web Crypto API.