Make line animations configurable: for instance, use fadein/out instead of line movement

[vlsi]

Samples: https://youtu.be/SIr7mcnVy98?t=2175 , https://youtu.be/SIr7mcnVy98?t=2195

The idea is that existing letters/words should move, while the new words/letters might have multiple appear animations: a) move from right (the current) b) move from left? c) fade in d) type-like animation (~fade in letter by letter as if it was typed)