Task: Get date in a YYYY-MM-DD format

n8n workflow JSON:
{"nodes":[{"name":"Function","type":"n8n-nodes-base.function","position":[860,440],"parameters":{"functionCode":"var date = new Date().toISOString().split('T')[0];\n\nitems[0].json.date_today = date;\n\nreturn items;"},"typeVersion":1}],"connections":{}}