Improve the ArkEmscripten playground #631

Is your feature request related to a problem?

The current playground is pretty bare, and the current method of capturing what's printed is not that good (though I have no clue how to make it better):

log = console.log;
var can_capture = false;

window.console.log = (message) => {
    log(message);
    if (can_capture)
        document.getElementById("output").value += message + "\n";
};

var Module = {
    onRuntimeInitialized: function () {
        document.getElementById("run").addEventListener("click", () => {
            document.getElementById("output").value = "";
            const code = document.getElementById("code").value;
            try {
                can_capture = true;
                Module.run(code);
            } catch (e) {
                document.getElementById("output").value = e;
            }
            can_capture = false;
        });
    }
};

Playground:

Describe the solution you would like

1. Improve the UI/UX of the playground (without having to add Vue, React or other huge libraries)
2. Add more utils / builtins to ArkEmscripten to play with DOM and JavaScript values / functions
3. Find a better way to get ArkScript output
4. Add more tests (currently not tested in the CI, only the compilation is tested)

Is it a big modification to the language? Leave it if you don't know

• Breaking change
• Compiler/syntax modifications
• Runtime modifications (standard library, modules, packages...)