Adding ability to have lint rules for JSONFile, exposing extension in…

[zsmoore]

• Please check if the PR fulfills these requirements

• [YES ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

#28

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) Exposes JSONFile to the linter, allows users to make lint rules for the file. Adds file extension to the JSONFile

• What is the current behavior? (You can also link to an open issue here) You can't lint on JSONFile

• What is the new behavior (if this is a feature change)? Lint rules for JSONFile can be created. File extension exposed

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?) getObject is no longer usable but should not have been used outside of library.

• Other information: