Variable support in the graph, passing variables to nodes

[MothDoctor]

There are plans but there's no reliable timeframe. It's not obvious which way to choose as a proper solution for all (at least most of) the projects. It could be

• blueprint-based variables
• blackboard-style
• blueprint-style, but using a method similar to @ryanjon2040 pull request: https://github.com/MothCocoon/FlowGraph/pull/86
• also might take inspiration from StateTree implementation in UE5

Flow Graph solution would need include support for UObject references.