Update highlights.md

culture/highlights.md

@@ -103,6 +103,7 @@ This is very much a living document, and likely missing things. so, please send
 - Aug 2018 - Artsy's public docs repo [is created][readme_init] - [RFC][docs_rfc] 🔒
 - Sep 2018 - The Artsy Omakase's name [is decided][oma_rfc]
 - Sep 2018 - Engineering highlights [are created][this_pr]
+- Oct 2018 - Buy now [is launched][buy_now]🔒
 
 <!-- prettier-ignore-start -->
 [helix-react]: http://artsy.github.io/blog/2015/04/08/creating-a-dynamic-single-page-app-for-our-genome-team-using-react/
@@ -194,3 +195,4 @@ This is very much a living document, and likely missing things. so, please send
 [cinder]: https://github.com/artsy/cinder#cinder
 [this_pr]: https://github.com/artsy/README/pull/50
 [neo-mp]: https://github.com/artsy/metaphysics/pull/809
+[buy_now]: https://artsy.slack.com/archives/C02BC3HEJ/p1539703456000100