Update posts/2018-11-02-semirings.md
Update posts/2018-11-02-semirings.md

Co-Authored-By: LukaJCB <3abedcbb9d0e7e92f361944360620f54a8d8e39c@fh-duesseldorf.de>
typelevel/typelevel.github.com,typelevel/typelevel.github.com,typelevel/typelevel.github.com