update Czech strings

[sorgoz]

Czech is not yet done, so there are three phrases;

  1. "Go to site" = "Pokračovat na stránku", if you mean "Go to this site" = "Pokračovat na tuto stránku"
  2. "Go back" = "Vrátit se zpět" or simply "Vrátit se", if you mean "Go to previous page" = "Vrátit se k předchozí stránce"
  3. "Leave the site" = "Opustit stránku", or "Leave this site" = "Opustit tuto stránku"

  Note: The word stránka or webová stránka is meaning website and also is apply to the word page in Czech language.

[sorgoz]

done