Add DOI to bibtex citation

[shancarter]

A comment from hacker news:
https://news.ycombinator.com/item?id=15648422

JorgeGT 1 hour ago [-]
Minor note, you should add the field DOI={10.23915/distill.00007} to the BibTeX citation. This is also missing from Google scholar, and is a particular pat peeve of mine now that DOIs are practically mandatory (copying the helpfully-formatted citation but then having to look around the page to find the DOI).

[ludwigschubert]

Fixed in 315e888!