documentation

Pull request #3792: [ZBXNEXT-9791] added parameters for MongoDB plugin, key for Zabbix agent2, updated What's New and Upgrade notes

Merge in WEB/documentation from feature/ZBXNEXT-9791-7.5-D to release/8.0

* commit 'd3dc0a76bb5eab8e830e9cb4d5648e597904c03f':
  [ZBXNEXT-9791] minor wording improvement
  [ZBXNEXT-9791] updated description for MongoDB plugin
  [ZBXNEXT-9791] updated MongoDB plugin description
  [ZBXNEXT-9791] added exception for parameter application sequence
  [ZBXNEXT-9791] added Parameter Application Sequence section
  [ZBXNEXT-9791] improved plugin description
  [ZBXNEXT-9791] improved plugin description
  [ZBXNEXT-9791] added parameters for MongoDB plugin, key for Zabbix agent2, updated What's New and Upgrade notes