"Log" mode for transitioning scalings

when interpolating values that represent a "zoom" or a scale, you need to transition the exponent, not the value.

Example:

If transitioning a graph scale from 100% to 1%, we don't want to do:
```
{ domain: [0, 1] } => { domain: [0, 0.01] }
```

instead we want:

```
{ scale: 0 } => { scale: -2 }
domain = [0, Math.pow(10, scale)]
```

Add a `log` mode for these transitions