SEO, engineering, and great content — Grammarly recently reached an ear-ringing valuation. After raising $200m last week, Grammarly officially became a $13bn-digital behemoth. The company rose to become one of the top 10 U.S. startups, according to Yahoo Finance. Grammarly helps 30 million students, digital professionals, and writers satisfy their 8th-grade English teacher’s expectations. I’ve checked…