Update Croatian translation

[milotype]

Please explain how to translate, or provide context for the following strings which I haven't translated:

• Staged
• #books created
• #books already found
• #books failed to import
• #books pending
• Referents
• Referrers
• Make Human
• Make Bot
• UnfollowFollow
• Library.link

[cdrini]

• This is used on our testing server to note which pull requests are currently loaded on testing and can be tested there. "Staged" is used to mean loaded and read for trying out -- google defines it as "planned, organized, or arranged in advance (often of an event or situation intended to seem otherwise).". I.e. staged on the testing server, before they'll eventually make their way to the fully public / production website.
  Staged

• Not sure...
  Referents
  Referrers

• These 4 are a short-hand for e.g. "Number of books created". They are displayed in the experimental new bulk import flow for importing books.
  #books created
  #books already found
  #books failed to import
  #books pending

• These are displayed in the admin dashboard. An admin can change a user's account type from a normal account "human" to a bot account, which has special privileges for things like running things in bulk.
  Make Human
  Make Bot

• "UnfollowFollow" These are for the new profile features. You can "Follow" another patron on open library, and you will be able to see the books they've logged, rated, etc (assuming they have this info public!). You can also unfollow to step seeing this info in your feed.

• This can stay as is, it's a third-party website.
  Library.link

[cdrini]

Awesome thank you @milotype ! merging this as is since it adds a ton of new translations 😊 Please don't hesitate to open a new PR for those last remaining strings!