docs: link into docs CI examples

[MikeMcC399]

Issue

The README document does not yet link to the document site's Continuous Integration > Introduction > Setting up CI > CI Docker examples section.

Change

Extend the README document to link to the Cypress document site's Continuous Integration > Introduction > Setting up CI > CI Docker examples section, which itself links to various examples of using Cypress Docker images in CI environments.

[MikeMcC399]

Preview

https://github.com/MikeMcC399/cypress-docker-images/blob/add/ci-example-link/README.md#examples

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