Add FormKitNode findUpwards() function

[mlmoravek]

Feature:

A FormKitNode element has the at(), find() and the walk() functions to walk through the subtree and find a particular node. For going upwards and searching there are only the parent and root properties.
However, I'm missing a function to walk up the tree until a node matches some condition.

I would like to have some function like findUpward() to find a node which is located up the tree of the current node.

[justin-schroeder]

Love the idea.