documentation

Merge branch 'release/7.0' of https://git.zabbix.com/scm/web/documentation into feature/DEV-3890-7.0-D. Merge conflict resolved in:
- /en/manual/api/changes_7.0.md (corrected version order);
- /en/manual/api/reference/alert/get.md (updated blockID);
- /en/manual/api/reference/mediatype/get.md for countOutput (caused by 96e231a42c8).