Add Charset Webpack Plugin

A Webpack and Rspack plugin that automatically prepends a @charset declaration to every emitted CSS file. Version 1.0.9 is the latest stable release with no active development cadence. It supports both CommonJS and ES modules, works with Webpack 4/5 and Rspack. Unlike manual CSS header additions or postcss plugins, it hooks into the compilation process to guarantee charset placement on all CSS assets with zero configuration overhead.