Support fail on duplicate key option

[ajj-stripe]

circe/circe#1130 was resolved for the Jawn parser (circe/circe#1149), but I don't believe this is the case for circe-yaml

Happy to be told I'm wrong, but would be very happy to see/use this feature with circe-yaml as well.

[ajj-stripe]

Implementation would probably involve adding a way to pass options to create a separate parser object, then having that parser object pass the relevant option(s) to SnakeYAML LoaderOptions

https://www.javadoc.io/doc/org.yaml/snakeyaml/latest/org/yaml/snakeyaml/LoaderOptions.html