Support other DDL Json formats

[DyfanJones]

Rstudio issue was raised around how json ddl's are created for AWS Athena:

• The confusion in how the DDL is created and what row format is accepted. This will mean an update to documentation is required.

• Can other json ddl formats be support with json line?

[DyfanJones]

Linking RStudio issue: https://community.rstudio.com/t/trying-to-get-athena-to-recognise-json-with-noctua-file-type/58971

[DyfanJones]

PR #85 adds support to appending to both JSON SerDe Libraries.