Better edge tooltips and added node outline dashes

Improved the triggering ease of edge tooltips by making invisible hoverable points larger for both edges and arrows.
The documentation explains how to override their properties (as well as how to have different tooltips for arrows and edges).
Added an argument for node outline dashes.

Full Changelog: v1.2...v1.3

More arguments for deeper customisation

Added arguments for marker and encode kwargs for each layer, allowing customisability without restrictions or safeguards; used them in an example in the tutorial notebook.
Added a node outline colour argument (defaulting to node_colour if None).
Added an edge dash argument.

Full Changelog: v1.1...v1.2

Scaling and padding without deforming

Added functionality around scaling and padding the chart while respectively matching and preserving aspect-ratios; new draw_networkx arguments: chart_width, chart_height, and chart_padding.
Added a copy_size_and_axes function to the default exports; it is useful to preserve the drawn aspect ratio when reassembling or concatenating layers with other charts, as shown in the last chart of the tutorial notebook.

Full Changelog: v1.0...v1.1

Full rework and new features

First release after determining it is reasonable for this project to be its own library (due to full and incompatible code base rework, new functionalities, and 4-year inactivity of the original project).
The new name, altair-nx, seems in fact the correct way round.