docs release v1.8.4

• Document the use of kubectl label for label handling (https://github.com/giantswarm/docs/pull/480)
• Add AWS CNI, Azure CNI and Flannel (https://github.com/giantswarm/docs/pull/482)
• Replace CoreOS with Flatcar (https://github.com/giantswarm/docs/pull/484)
• Configure crd-docs-generator via a config file, rather than command-line flags (https://github.com/giantswarm/docs/pull/485)
• Add information regarding a CoreDNS breaking change (https://github.com/giantswarm/docs/pull/486)
• Fix a font warning in the Firefox browser (https://github.com/giantswarm/docs/pull/487)
• Add the new --output flag to the gsctl list nodepools command (https://github.com/giantswarm/docs/pull/488)
• Remove the mention that gsctl list clusters returns all clusters with JSON output (https://github.com/giantswarm/docs/pull/489)