tsconfig.json

{
  "compilerOptions": {
    "target": "es2017",
    "module": "commonjs",
    "lib": ["es6", "dom", "esnext"],
    "allowJs": true,
    "checkJs": false,
    "jsx": "react",
    "sourceMap": true,
    "outDir": "./build",
    "removeComments": true,
    "importHelpers": true,

    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictBindCallApply": true,
    "strictPropertyInitialization": true,
    "noImplicitThis": true,
    "alwaysStrict": true,

    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,

    "moduleResolution": "node",
    "esModuleInterop": true,

    "typeRoots": ["node_modules/@types", "node_modules/web-ext-types"],

    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  },
  "include": [
    "src"
  ]
}