GNNGraphs-v1.4.2

Diff since GNNGraphs-v1.4.1

Merged pull requests:

• port GNNGraphs tests to TestItems.jl (#573) (@CarloLucibello)
• add reference to PyGDatasets (#578) (@CarloLucibello)
• fix GNNGraphs zygote error (#579) (@CarloLucibello)
• bump KrilovKit (#587) (@CarloLucibello)
• better inference for num_nodes (#588) (@CarloLucibello)
• fix corner case in normalize_graphdata (#589) (@CarloLucibello)

Closed issues:

• GNNGraph default num_nodes to length of element of ndata (#581)
• Can't have empty edata for graph with no edges (#582)