Jupyter-scatter

- Take the x-padding into account when setting a fixed width ([36](https://github.com/flekschas/jupyter-scatter/issues/36))
- Make `width` and `height` correspond to the canvas' (i.e., inner) dimensions such that `Scatter(width=500, height=500)` will lead to a canvas of size 500x500 px.

- Add support for legends via `scatter.legend(True, position='top-right', size='small')` ([30](https://github.com/flekschas/jupyter-scatter/issues/30))

- Remove accidentally added `console.log`

- Add support for axes labels via `scatter.axes(labels=True)` or `scatter.axes(labels=['x-axis', 'y-axis'])` ([29](https://github.com/flekschas/jupyter-scatter/issues/29))

- Fix issues when specifying the color, opacity, or size map via a `dict`

- **Breaking changes:**
- For `scatter.color()`, rename `color` to `default`, `color_selected` to `selected`, and `color_hover` and `hover`
- For `scatter.opacity()`, rename `opacity` to `default`
- For `scatter.size()`, rename `size` to `default`
- For `scatter.connection_color()`, rename `color` to `default`, `color_selected` to `selected`, and `color_hover` and `hover`
- For `scatter.connection_opacity()`, rename `opacity` to `default`
- For `scatter.connection_size()`, rename `size` to `default`
- Add `scatter.opacity(unselected=0.5)`. This property defines the opacity scaling factor of unselected points and must be in `[0, 1]`. This scaling is only applied if one or more points are selected.