fix: quote yaml string with colons

Author: systematicguy

_data/conferences.yml

@@ -9,7 +9,7 @@
   sponsor: https://www.python-summit.ch/sponsoring/
   twitter: pythonsummit
   sub: PY
-  note: Day 1: General Language Topics; Day 2: Data Science Topics
+  note: "Day 1: General Language Topics; Day 2: Data Science Topics"
   location:
       latitude: 47.223987
       longitude: 8.817300