documentation

Pull request #1339: feature/ZBX-22818-6.0-D: Added support for last_foreach in aggregate functions.

Merge in WEB/documentation from feature/ZBX-22818-6.0-D to release/6.0

* commit 'cf0ee742411c5c43a44db9db1551cdd9c875c713':
  [ZBX-22818] Refined "What's new" entry to emphasize what's actually new
  [ZBX-22818] Added support for last_foreach in aggregate functions