fscreen: Cross-Browser Fullscreen API

fscreen is a small, vendor-agnostic JavaScript utility library that provides a unified interface to the browser's Fullscreen API. It abstracts away browser-specific prefixes (like `webkit` or `moz`) for methods and properties such as `requestFullscreen`, `exitFullscreen`, `fullscreenElement`, and event listeners like `fullscreenchange` and `fullscreenerror`. The current stable version is 1.2.0. As a lightweight wrapper, fscreen aims to simplify cross-browser fullscreen implementation without introducing significant overhead or polyfills. It doesn't have a strict release cadence, typically releasing new versions as needed to adapt to browser changes or fix issues. Its primary differentiator is its simplicity and focus on providing a direct, standardized access layer to the native Fullscreen API, ensuring consistent behavior across different browsers without requiring developers to manage vendor prefixes manually.