Moving to Core Cypress Repo

In an effort to better maintain and enhance this official plugin, we will be moving it into the [main Cypress repo](https://github.com/cypress-io/cypress) sometime in the next few weeks. During that time, we will be going through issues and PRs to make sure all relevant items are moved over and labeled appropriately.

Once it is moved, this repo will be archived and will become read-only.

This issue is a repository-migration announcement rather than a contribution task. Start by reviewing the linked main Cypress repository and the current cypress-io/code-coverage repository status. The stated outcome is that relevant issues and pull requests move to the main repo and this repository becomes read-only.

Written by the indexing model from the issue text.