documentation

Pull request #1824: feature/ZBXNEXT-8956-7.0-D. Enabled communication framework for existing widgets.

Merge in WEB/documentation from feature/ZBXNEXT-8956-7.0-D to release/7.0

* commit '0ec8aad293727eff90e339b753e730a403f0c170':
  [ZBXNEXT-8956] updated note and list formatting
  [ZBXNEXT-8956] fixed blockIDs
  [ZBXNEXT-8956, ZBXNEXT-8145] the scope of feature-related template changes is wider
  [ZBXNEXT-8956] added template-related changes; moved "Template changes" page contents to "What's new" and "Upgrade notes" pages
  [ZBXNEXT-8956] updated wording & formatting
  [ZBXNEXT-8956] reverted table formatting-related changes
  [ZBXNEXT-8956] enabled communication framework for existing widgets