fix: replaceEsm typings

Currently:

```ts
// `subscriptions` is `void`
const subscriptions = await td.replaceEsm(
      '../../subscriptions.js',
);
```

Now:

```ts
// `subscriptions` is `{ [namedExport: string]: any; default?: any; }`
const subscriptions = await td.replaceEsm(
      '../../subscriptions.js',
);
```

Improve replace typings

…denext

Add `types` export condition

For a TypeScript project that has `moduleResolution: "nodenext"` set, TypeScript won't respect the existance of an `index.d.ts` when providing type definitions for a module.

Explicitly adding the `"types"` condition in the export definition, as supported by TypeScript 4.7 and later, resolves this problem.

…n-return

Add `thenReturn` to `PromiseStubber` type declaration

To ensure that `PromiseStubber.thenReturn` will compile

This allows you to stub an async function with a sequence of
promises that may either resolve or reject

…isn't available locally and I need to cut a release)