fix slash div warning according to sass spec https://sass-lang.com/d/slash-div
fix slash div warning according to sass spec https://sass-lang.com/d/slash-div

hb-gatsby/gatsby-starter-lumen,alxshelepenok/gatsby-starter-lumen,wpioneer/gatsby-starter-lumen,ochaloup/blog.chalda.cz,ochaloup/blog.chalda.cz,alxshelepenok/gatsby-starter-lumen