TypeScript definition of act() function allows Promise as a parameter, but code fails if Promise is provided

[cbxp]

https://github.com/testing-library/svelte-testing-library/blob/5ae96a77c7c4f80183ed89908482dc4b88059ae6/src/pure.js#L94

The code above should check if fn is a function before calling it, otherwise should be used as a Promise