tLN: Export function to create supervision

[danyill]

I'd like to be able to create supervision LNs without having to instantiate them.

This might be as a first step to creating a scheme where a certain number of supervisions are known to be required.

If we could export createSupervisionEdit as follows that would be one way of achieving this.

scl-lib/tLN/supervision/createSupervisionEdit.ts

Line 108 in f67d73d

function createSupervisionLogicalNode(