Migrate to ESM

## What would you like?

Migrate this repo from CommonJS to ESM, currently

https://github.com/cypress-io/github-action/blob/e0f7da8ca6019174b8b2a507657cd282c2e22023/package.json#L36

## Why is this needed?

Key dependencies in this repo have moved or will move to ESM, for example:

- GitHub Actions [toolkit `@actions/*`](https://github.com/actions/toolkit) modules ~~are expected to move~~ have moved to ESM ~~soon~~
- [got](https://www.npmjs.com/package/got) is locked at `11.8.6` because `got@>=12` is native ESM.
> Got v11 is no longer maintained and we will not accept any backport requests.