Update options for all headless browsers to change screen size (#3035)
Update options for all headless browsers to change screen size (#3035)

* Update options for all headless browsers to change screen size

- Add note about us being in cypress/plugins/index.js file since people
just jump to the section they need and don’t know where to add the code.

* Add warning indicating this is different from `viewportHeight` and `viewportWidth`

* Add link to configuration
cypress-io/cypress-documentation,cypress-io/cypress-documentation