fix: add tsconfig.json for playwright tests

fix: add tsconfig.json for playwright tests

1. Avoid "The file must be included in at least one of the projects
provided" error when using type-aware ESLint configurations;
2. It's recommended by the [playwright documentation](https://playwright.dev/docs/test-typescript#tsconfigjson):
> We recommend setting up a separate `tsconfig.json` in the tests
directory so that you can change some preferences specifically for the
tests.