documentation

[ZBXNEXT-9232] Enhance visibility with sparkline chart API documentation

Merge in WEB/documentation from feature/ZBXNEXT-9232-7.2-D-API to release/7.2

* commit '642f35f74bcef8b6cfdb2fa2e631b0c16bc481e6':
  updated API changes entry
  [ZBXNEXT-9232] grammatic improvements to changes.md
  [ZBXNEXT-9232] fixed order after merge from release/7.2-D
  [ZBXNEXT-9232] fixed relative urls on api changes page
  [ZBXNEXT-9232] updated api changes page
  [ZBX-9232] added missing description for color; fixed table columns width issues
  [ZBXNEXT-9232] formatting fixes
  [ZBXNEXT-9232] updated API documentation for item_value and top_hosts widgets