StringDecoder for Userland

The `string_decoder` package provides a userland implementation of the Node.js core `string_decoder` module. It is designed to correctly decode `Buffer` objects into strings, specifically handling multi-byte UTF-8 and UTF-16 characters that may span across multiple buffer chunks. This prevents issues like malformed characters when processing streamed or chunked data. Maintained by the Node.js Streams Working Group, it offers a stable and reliable solution for character decoding outside of the core Node.js environment. The current stable version is 1.3.0, released 7 years ago, indicating its maturity. Prior to version 1.0.0, its versions mirrored those of Node.js core; since 1.0.0, it adheres to Semantic Versioning. Its key differentiator is being a direct, semantically versioned mirror of the high-performance Node.js core implementation, making it suitable for environments where Node's built-in module is not directly available or a specific version parity is required, such as in browserify bundles.