UHF-9309 link to static copy of the site

[dire]

UHF-9309

What was done

• Added a link leading to the copy of the site to the maintenance page.

How to install

• Make sure your etusivu instance is up and running on latest dev branch.
  • git pull origin dev
  • make fresh
• Update the HDBT theme
  • composer require drupal/hdbt:dev-UHF-0000_insert_correct_branch
• Run make drush-locale-update drush-cr
• Run drush state:set system.maintenance_mode 1 --input-format=integer to put the site to the maintenance mode.

How to test

• Open https://helfi-etusivu.docker.so/en and check that there is now a link to the static copy of the site.
• Open https://helfi-etusivu.docker.so/fi and https://helfi-etusivu.docker.so/sv to check that the translations work.
• Check the maintenance page in any of the alternative language, for example: https://helfi-etusivu.docker.so/uk. The links and the H1 title should now have correct fallback lang and dir attributes.
• Check that code follows our standards.

Designers review

• This PR does not need designers review
• This PR has been visually reviewed by a designer (Nina Hiukkanen)

[khalima]

Good job! Let's merge this. 🚀