Implement multiple languages support

[Mateusz-Dobrzynski]

Acceptance Criteria

• In translatable pages (i.e. not in articles) the content changes depending on the selected language
• Polish and English are fully supported (i.e. translations for currently available content are added)
• The language is automatically changed depending on the user browser settings (Polish in case of Polish and English in all other cases)
• The user can manually change the site language using a button present in the top navigation bar
  • On desktop: Languages icon and language name
  • On mobile: Languages icon only (https://lucide.dev/icons/languages)

To do:

• Check possible solutions provided by astro