documentation

[ZBXNEXT-5491] Updates for renaming data sets in Graph widget.

Merge in WEB/documentation from feature/ZBXNEXT-5491-6.4-D to release/6.4

* commit 'ee2d931bb6a4f91ea8d50940dc3f79c349cd992e':
  [ZBXNEXT-5491] Updated "What's new" after resolving merge conflict
  [ZBXNEXT-5491] Updated style; additional images
  [ZBXNEXT-5491] Updates for renaming data sets in Graph widget