Add schema testing
Add schema testing

This application contains schema tests, but they're not run for PRs on
alphagov/govuk-content-schemas.

This adds a jenkins shell script so they can be run by:

https://ci.dev.publishing.service.gov.uk/job/govuk_multipage_frontend_sc
hema_tests

alphagov/multipage-frontend,alphagov/multipage-frontend,alphagov/multipage-frontend