[docs] groundwork for version dropdown about red-hat-design-system

[hellogreg]

Related: #1485

[zeroedin]

For PFE we are deploying these sites to two different domains then there is redirects in netlify.toml

[[redirects]]
  from = '/v1/*'
  to = 'https://release-v1--patternfly-elements.netlify.app/:splat'
  status = 200
  force = true

[[redirects]]
  from = '/v2/*'
  to = 'https://release-v2--patternfly-elements.netlify.app/:splat'
  status = 200
  force = true

There was talk awhile back about moving the ux. domain to netlify is this still possible @markcaron ? If so would make versioning the site much like we do in patternfly elements easier.

Otherwise we'll have to modify CI to checkout and build these versions of docs and push them to subdirectories, although I figure we'll run into issues with node versions on build doing so unless you can split actions to different environments.