Generate IDs for paths for better performance

[BenJeau]

This is not currently a problem, but with #46, if this is not implemented, it will become a problem since the keys for SVG paths is simply the index, and it will not be linear like it is right now once layering is implemented.

Implementation

Generate a random ID and add it to the path:

• UUID, but this would required extra dependencies (probable what should be done (would require uuid and react-native-get-random-values
• Current time (most simple), but if multiple people "draw" on the same Canvas, there would be collisions
• The path itself, but there may a problem if it happens that the user draw the exactly same path

[BenJeau]

I think that the current time that the stroke was drawn is a good addition and we should still add a uuid to the paths or a counter (but a uuid would be easier implementation-wise)