Fish Shell 4.0 Released: Core Code Ported to Rust

Fish shell 4.0 is now available, featuring a core codebase ported from C++ to Rust. While this significantly changes dependencies and build processes, end-users should experience minimal disruption. The release boasts numerous improvements, including enhanced key bindings, terminal support, and scripting capabilities, alongside some backward-incompatible changes. Noteworthy changes include the default enabling of `qmark-noglob`, the replacement of `%self` PID expansion with `$fish_pid`, and the ability to build Fish as a self-installing binary for easier deployment.