Split out a GraphsBase package?

[CarloLucibello]

Graphs.jl is not an heavy packgage, but still it adds 1 or 2 secs to the latency of packages depending on it (my use case is GraphNeuralNetworks.jl).

There would be some interest in moving the function definitions needed to define a custom graph type https://juliagraphs.org/Graphs.jl/dev/ecosystem/interface/ and possibly a few more to a separate lean package (similarly to what StatsBase.jl, DataAPI.jl, ChainRulesCore.jl do)?

[gdalle]

I for one am very much in favor of that

[gdalle]

@etiennedeg I can set it up if you want to move your new interface code there?

[gdalle]

It's alive at https://github.com/JuliaGraphs/GraphsBase.jl, still waiting to find time to review the first ginormous PR