Support ancillary data inputs

[rezonant]

As best I can tell, macadam does not yet support ancillary data inputs. Certain Decklink models support VANC (HANC is not supported). Blackmagic's Decklink SDK documentation covers this in section 2.4.7.

I hope to give a shot at implementing it, provided it isn't already in progress elsewhere.

[sparkpunkd]

No ANC support yet and I'm not aware of it being on any roadmap. We did add some timecode support but not ANC. You are very welcome to try to implement and would be pleased to consider a pull request.

[rezonant]

Work in progress on https://github.com/rezonant/macadam/tree/feat/ancillary-data