Issue with Typescript `import utc from "dayjs/plugin/utc"` gives Cannot find module 'dayjs/plugin/utc' or its corresponding type declarations

**Describe the bug**
I got `Cannot find module 'dayjs/plugin/utc' or its corresponding type declarations` when using Typescript and dayjs latest version.

**Expected behavior**

I fixed this using :
```typescript
import utc from "dayjs/plugin/utc.js";
```
(with .js suffix) but I don't know I'm supposed to do so.

No source file or test is named. Reproduce the TypeScript import failure with the latest Day.js package, then inspect how the utc plugin is exposed and resolved; done when the intended import form works consistently or the required .js suffix is clearly documented.

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