Add VegaLite widget integration

[jonatanklosko]

Further work towards #189.

See Kino.VegaLite and the demo notebook.

kino.mp4

[jonatanklosko]

I made this as a LV instead of component after all, so that the widget server can detect once it goes down by monitoring it.

[josevalim]

Exciting! I have dropped some comments. If you want to discuss any of these things in particular, please let me know.

I have only one remaining nitpick. Should we call it LiveWidget or Livewidget? I think it is already a bit confusing that we have Livebook and LiveView with different casings but I think it is understandable, they are effectively separate "products". But I think adding LiveWidget will make things more confusing...

Alternatively we give it another name altogether... maybe something that stays closer with the livebook/notebook nameset?

[josevalim]

We can also just call it something else altogether. Here is a suggestion: Kino - Interactive widgets for Livebook. It is short and has good etymology:

kino-

before vowels, kin-, word-forming element in use from late 19c. and meaning "motion," from Greek kino-, from kinein "to move" (from PIE root *keie- "to set in motion").

• https://www.etymonline.com/word/kino-#etymonline_v_42966

Also flip books were known as kinographs, which is the closest we get to an animation in a book. :)

[Benjamin-Philip]

Just FYI, the word "kino" refers to a sort of gum used for tanning. See https://g.co/kgs/K6dHiQ. That might be worth taking into consideration.

However when most people think of kino, it relates to films and cinema. Which is what we are trying to go for.

+1 for kino.

[jonatanklosko]

@josevalim I wanted to discuss the LiveWidget name anyway, Kino sounds absolutely great to me!

[josevalim]

I dropped one comment and this looks good to go!