added note about Firefox and Edge (#3182)
added note about Firefox and Edge (#3182)

Co-authored-by: Jennifer Shehane <b76474446821c6f7360e4eee990dc1f8d635e16a@gmail.com>
Co-authored-by: Jennifer Shehane <e3cd9f6469fc3e1acfb9f2bdbfc5a3d2bbb8e2ad@cypress.io>
cypress-io/cypress-documentation,cypress-io/cypress-documentation