[Feature Request] Call undirected edges in FGL.ArrayAdjacencyGraph

[LibraChris]

At the moment in order to call an edge you need to call the edge with a designated source and target (As explained in #50 ). Adding functionality to call edges independent from this source/target designation will allow for easy calling of undirected edges.

[LibraChris]

• [x] Add simple functions to call undirected edges(#58 )

• [ ] Add functions to edit undirected edges

• [ ] Add functional calls for undirected edges