chore: add beginning of migration guide for Cypress 15#6159

AtofStryker merged 4 commits intorelease/15.0.0cypress-io/cypress-documentation:release/15.0.0from

chore/add_angular_17_ct_removal_docscypress-io/cypress-documentation:chore/add_angular_17_ct_removal_docsCopy head branch name to clipboard