riot-web/.babelrc

{
    "presets": [
        "@babel/preset-react",
        ["@babel/preset-env", {
            "modules": false,
            "targets": {"browsers":  ["last 2 versions"]}
        }],
        "@babel/preset-flow",
        "@babel/preset-typescript"
    ],
    "plugins": [
        "babel-plugin-add-module-exports",
        "@babel/plugin-proposal-numeric-separator",
        "@babel/plugin-proposal-class-properties",
        "@babel/plugin-proposal-object-rest-spread",
        "@babel/plugin-transform-flow-comments",
        "@babel/plugin-transform-async-to-generator",
        "@babel/plugin-transform-runtime",
        "@babel/plugin-syntax-dynamic-import"
    ]
}