Allow configuring diagram direction

[keyserj]

Describe your issue

Sometimes it's nice to read edges from solutions to problems, but sometimes it seems like it'd be nice to read the other way too. Particularly it could be nice to read edges top-down instead of bottom-up (e.g. instead of bottom-up solution-addresses-problem, use top-down problem-addressed-by-solution).

Similarly, sometimes it's nice to have problems laid out at the top of the diagram, with solutions on the bottom, but other times it'd be nice to invert this (maybe when the focus is intended to be on solutions, like for proposals).

Solution you'd like

Add configuration to allow these different options:

• problems on top, solutions on bottom, edges reading bottom-to-top (current)
• problems on top, solutions on bottom, edges reading top-to-bottom
• solutions on top, problems on bottom, edges reading bottom-to-top
• solutions on top, problems on bottom, edges reading top-to-bottom

Alternatives you've considered

No response

Additional context

• related #154

Technical ideas and questions

• edge direction seems like it could easily be hacked within the edge component itself, with a map of edge type to reversed edge type. seems like it'd be a lot of not-worth work and complexity to actually refactor source and target everywhere
• reversing the node layout would require reversing partitions. maybe the layout could just swap all sources and targets so we don't need to add complexity to everywhere that uses source and target?