tsconfig.json

{
  "compilerOptions": {
    "target": "es2018",
    "lib": ["es2018", "dom"],                             /* Specify library files to be included in the compilation. */
    "allowJs": true,                       /* Allow javascript files to be compiled. */
    "checkJs": true,                       /* Report errors in .js files. */
    "declaration": true,
    "outDir": "./dist",
    "rootDir": "./",
    "emitDeclarationOnly": true,
    "strict": false,
    "noImplicitAny": false,
    "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
    "paths": {
      "y-codemirror": ["./src/y-codemirror.js"]
    },
    "maxNodeModuleJsDepth": 0,
    "allowSyntheticDefaultImports": true
  },
  "include": ["./src/y-codemirror.js", "./demo/codemirror.js"]
}