UHF-4571: Hel.fi favicons

[Arkkimaagi]

UHF-4571

Current favicons are transparent and cause problems with dark browser skins. They do not behave well with all use-cases as some files are missing. This updates favicons to proper format.

What was done

• Added relevant favicon files
  • And updated them to latest HDS favicons
• Added source files
  • HDS handles these on their end
• Added instructions on how to create files from source files and documentation on how to use said files
  • HDS handles these on their end
• Added html code to use the files

How to install

• Make sure your 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-4571_favicons
• Run make drush-updb drush-cr

How to test

• Check that favicons work in all contexts that you can think of
• Check that favicon follows HDS guideline in using dark version in dark mode (where svg is supported)
• Check that code follows our standards

Designers review

• This PR does not need designers review
• This PR has been visually reviewed by a designer (Name of the designer)

[teroelonen]

Technical implementation works perfectly 🦖

[Arkkimaagi]

I'll discuss about the wanted design with Mari K before we proceed with this.

[Arkkimaagi]

Updated latest HDS favicons to this PR that were generated due to the discussions started by this PR