feat: filename in meta

[jjagielka]

Would it be possible to add to meta the currently processed file name? I would be able, for example, to add links to GitHub directing straight to the file.

{
  "Wrapper": "/src/routes/utils/ExampleWrapper.svelte",
  "example": true,
  "file": "/src/pages/my_component_doc.md"
}

[mattjennings]

@jjagielka sorry for the late response on this. I've added this as filename and it'll be available in 0.4.0 which I plan to publish today

#27