fix :add missing onyx-sql dependency

Author: vladfaust

content/posts/creating-json-apis-with-onyx-part-2.md

@@ -103,6 +103,9 @@ dependencies:
  onyx-rest:
  github: onyxframework/rest
  version: ~> 0.6.3
+ onyx-sql:
+ github: onyxframework/sql
+ version: ~> 0.6.2
  pg:
  github: will/crystal-pg
  version: ~> 0.15.0