#834 Using & as a separator for the multiple nodes

[knsv]

📑 Summary

Adding & as a separator for having multiple nodes in one statement as in:

graph LR
        a --> b & c--> d

Here is the diagram above with the old syntax:

graph LR
        a --> b
        a --> c
        b --> d 
        c --> d

Resolves #834

📏 Design Decisions

Which character to use as a separator is important. It was a amtch between & and , but , is a valid charatcer in a node id so therefore & was chosen.