Add Debug Adapter Protocol Support to GJS

GJS is a JavaScript runtime built on Firefox's SpiderMonkey JavaScript engine and the GNOME platform libraries. It allows the use of the GNOME platform libraries in JavaScript programs. GJS powers GNOME Shell, Maps, Characters, Sound Recorder and many other apps. The Debug Adapter Protocol (DAP) defines the abstract protocol used between a development tool (e.g. IDE or editor) and a debugger. DAP makes it possible to implement a generic debugger for a development tool that can communicate with different debuggers via Debug Adapters. DAP is already supported by the most prominent code editors and tools like VS Code, Zed, Emacs, etc… (https://microsoft.github.io/debug-adapter-protocol/implementors/tools/) Today, you can already debug applications and libraries written for/with Android, Node.js, Deno, C, C++, Rust, Python and more (https://microsoft.github.io/debug-adapter-protocol/implementors/adapters/). This proposal aims to make GJS applications and libraries like GNOME Shell, Maps, Decibels etc… debuggable by implementing a DAP adapter for GJS.