Clarify contacts details for publishers and consumers

Changes to make contacting publishers and requesting a new publication easier

• Updated copy for Support page - #799
• Clarity for dataset contact links - #769

Technical updates

• Updated markup for homepage - #778
• Dependabot config - #780

Gem updates

• faraday - #747
• elasticsearch - #757
• secure_headers - #777
• govuk_publishing_components - #782
• govuk_elements_rails - #784
• rubocop - #788
• govuk_publishing_components - #791
• Rubocop error fixes - #800