Investigate adding in additional annotations

[evinism]

Right now, tinybaker has only one annotation, e.g. fileset::. We might want to leverage the idea to help with interface stuff.

Potential things!
pkl::
json::
xml::
pd::

Enabling things like:

def script(self):
  self.input_files["model"].predict(self.input_files["data"])
  self.output_files['model'] = lololol

i'm not sure what the final endpoint of this will be, but it'll be good to start thinking about it. Might inform future API work too.