Need a link to Annotated formulas from Getting started guide

[epogrebnyak]

Getting started guide at https://distill.pub/guide has a section for Formulas, but no link to Annotated formulas https://github.com/distillpub/template/wiki/Annotated-Formulas, which are visible in https://distill.pub/2018/editorial-update/#best-practices.

Annotatated formulas are great, we need a link to them from https://distill.pub/guide. I was trying to find them on a website for quite a while before I remembered they were linked in editorial-update.