tsconfig.json

{ 
  "extends": "@tsconfig/svelte/tsconfig.json",
  "compilerOptions": {
    "module": "esnext",
    "target": "esnext",
    "jsx": "preserve",
    "allowSyntheticDefaultImports": true,
    /* more strict checking for errors that per-file transpilers like `esbuild` would crash */
    "isolatedModules": true,
    /* noEmit - We only use TypeScript for type checking. */
    "noEmit": true,
    /* Additional Options */
    "strict": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "resolveJsonModule": true,
    "useDefineForClassFields": true,

    // You can't currently define paths in your 'extends' config,
    // so we have to set 'baseUrl' & 'paths' here.
    // Don't change these unless you know what you're doing.
    // See: https://github.com/microsoft/TypeScript/issues/25430
    "baseUrl": "./",
    "paths": { "*": ["web_modules/.types/*"] },

    "types": ["snowpack-env", "svelte", "jest", "@testing-library/jest-dom"]
  },
  "include": ["src", "types"],
  "exclude": ["node_modules"]
}