Draft: Use DataViews for post-meta and custom sources block bindings.

[cbravobernal]

What?

Experiment checking how could DataViews work for post-meta and custom sources.
Right now it is hard-coded on block bindings, but I'll think about how to make it extensible. We could:

• Have a DataView per source, separated by tabs.
  

• Have a big DataView with all sources.
  

Demo:

dataviews_demo_mp4.mp4

[github-actions]

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