docs release v1.8.0

Apr 30, 2020 Documentation docs v1.8.0

Adapt search to work with Elasticsearch 6.8 https://github.com/giantswarm/docs/pull/411
Skip some CRDs when publishing CRD docs https://github.com/giantswarm/docs/pull/476
Fix some links https://github.com/giantswarm/docs/pull/474

This part of our documentation refers to our vintage product. The content may be not valid anymore for our current product. Please check our new documentation hub for the latest state of our docs.