tsconfig.json

{
    "compilerOptions": {
        "noImplicitAny": false,
        "noEmitOnError": true,
        "removeComments": true,
        "experimentalDecorators": true,
        "sourceMap": true,
        "target": "esnext",
        "lib": [
            "es2017",
            "dom",
            "dom.iterable",
            "esnext.asynciterable",
            "webworker"
        ],
        "module": "esnext",
        "strictNullChecks": false,
        "jsx": "react",
        "jsxFactory": "h",
        "skipLibCheck": true,
        "plugins": [
            {
                "name": "typescript-lit-html-plugin",
                "tags": [
                    "html",
                    "svg",
                    "raw"
                ]
            }
        ],
        "emitBOM": true,
        "charset": "utf8",
        "outDir": "build",
        "baseUrl": ".",
        "paths": {
            "lit-element": ["./node_modules/lit-element/lit-element"]
        }
    },
    "exclude": [
        "bin",
        "lib"
    ],
    "compileOnSave": true
}