[todo] convert project to monorepo structure

[nberlette]

This is a tracking issue for the lz4-wasm project's conversion to a new
monorepo-style workspace structure. The goal is to simplify the project, improve
long-term maintainability, and enhance the development experience, while
ensuring that all existing functionality remains intact.

I've decided to move this project into a monorepo format in anticipation of
future features that are currently in development. This will allow better
organization, and separation of concerns, and will facilitate easier testing and
development of each component independently.

Modules

Entry Point	Description
./packages/lz4	Primary public API, runs with ./lz4-wasm or ./lz4-cli.
./packages/lz4-cli	Command-line interface for LZ4 compression and decompression.
./packages/lz4-wasm	WebAssembly bindings for LZ4 compression and decompression.
./playground	Source for the LZ4 Playground web application.