documentation

Pull request #1996: feature/ZBX-24554-7.0-D. documented improvements and fixes for Item history widget.

Merge in WEB/documentation from feature/ZBX-24554-7.0-D to release/7.0

* commit 'efe41fdde87f5068e33c721e3f6128aabd6ec1e5':
  [ZBX-24554] documented improvements and fixes for Item history widget