Fix list of previous years

README.adoc

@@ -6,6 +6,7 @@ The easiest way to run these is using docker – simply execute `run.sh <day&
 the specific day.
 
 I have separate repositories for solutions from previous years:
+
  - https://g.c5h.io/archive/aoc-2018[2018] (Nim)
  - https://g.c5h.io/archive/aoc-2017[2017] (Python)
  - https://g.c5h.io/archive/aoc-2016[2016] (Python)