Rename rendering function! about altair

[g3o2]

Why not name the function after the already familiar vega_embed? vega_widget would be a good name for a helper function.

Given the $schema property, vega-embed 3 automatically recognizes vega3/4/... and vega-lite2/... specs. So vega-lite() as a render function would no longer be needed.

[AliciaSchep]

I like the idea of also naming the main render function vegawidget (or vega_widget). I see widget as referring to the fact that the function is creating an htmlwidget, which is a higher level thing than just vega_embed in R terms. Since the function could also take in vega specs in addition to vegalite specs, the name vegalite would be less appropriate.

[ijlyttle]

Going on my to-do list! vegalite() will be deprecated in favor of vegawidget(). If (when) this becomes its own package, I think it would be useful to have the package name to be the same as the function name.