Support Rojo project files

[Anaminus]

With a few additions, an rbxmk script can be written to parse a Rojo project and compile the result, and vice-versa. This could be used to integrate more easily with existing projects, and aid transitions between Rojo and rbxmk.

This could be implemented as a script, but could also be a sub-command for better UX.

Dependencies

• Add generic JSON format #40: Add generic JSON format
• Integrate command flags #33: Integrate command flags (if command)

References

• https://rojo.space/docs/

TODO

• Explore implementation details