Fix Croatian translation

[marin-marsic]

This is a Hacktoberfest contribution.

Fixes for croatian translation:


1. Wrong word was used to translate “browser”. Word “tražilica” (search engine) was used instead of “preglednik” (browser)
2. Fixed a couple of typoes
3. Removed “many” form from plurals because it is not relevant in Croatian language.
4. Made translation more consistent using informal wording. In some places, formal version of “you” was used, while in most places informal version was used. I’ve checked other languages (German) to make sure they are also using informal wording.