documentation

Merge branch 'release/7.0' of https://git.zabbix.com/scm/web/documentation into feature/ZBXNEXT-8145-7.0-D2-API. Merge conflict caused by DEV-3099, and resolved in en/manual/api/reference/dashboard/widget_fields:
- action_log.md
- gauge.md
- graph_classic.md
- graph_prototype.md
- graph.md
- item_value.md
- pie_chart.md
- plain_text.md
- top_triggers.md
- url.md