ruffle/web/packages/core/tsconfig.json

{
    "extends": "@tsconfig/recommended/tsconfig.json",
    "compilerOptions": {
        "module": "esnext",
        "moduleResolution": "node",
        "target": "es6",
        "strict": true,
        "outDir": "pkg",
    },
    "include": ["src/**/*"],
}