Describe the bug
Error when building any code using @V3.
No "exports" main defined in @actions/core/package.json

To Reproduce
Try to build this code:

import { setOutput } from '@actions/core';
setOutput('x', 1);

Expected behavior
Code should build as normal.

Screenshots
n/a

Desktop (please complete the following information):

• OS: [e.g. iOS] linux
• Browser [e.g. chrome, safari] n/a
• Version [e.g. 22]

Additional context
Add any other context about the problem here.