tsconfig.json

{
    "compilerOptions": {
        "allowJs": true,
        "alwaysStrict": true,
        "checkJs": false,
        "downlevelIteration": false,
        "inlineSources": false,
        "lib": ["es2015", "es2016", "es2017", "es5", "es6", "esnext", "dom"],
        "module": "es6",
        "noFallthroughCasesInSwitch": true,
        "noImplicitAny": true,
        "noImplicitReturns": true,
        "noImplicitThis": true,
        "noUnusedLocals": true,
        "noUnusedParameters": false,
        "outDir": ".",
        "removeComments": true,
        "sourceMap": false,
        "strict": true,
        "strictNullChecks": true,
        "target": "es2017",
        "typeRoots": ["@types", "node_modules/web-ext-types"]
    },
    "files": ["src/background.ts", "src/options.ts", "src/popup.ts"]
}