[BUG]Editing story: can't edit value.

[reuse-ay]

Describe the bug

In editing story, I can't edit cell values.

To Reproduce

Steps to reproduce the behavior:

1. Go to editing story
2. Double click on "First value" or "Second value". (Nothing happens)

Expected behavior

Double-click the text to make it editable.
mxgraph example

maxgraph@0.13.0

Additional context

I've used editing in my personal projects, so perhaps it's just a problem with the story.

[reuse-ay]

In story, MyCustomGraph (extends Graph) .getLabel return HTMLTableElement, but in Graph, return of getLabel should be string. So an error occured. To fix this, a number of changes are needed.

[tbouffard]

Hi I reproduced the problem.

In mxGraph, mxGraph.getLabel returns string | Node (https://github.com/typed-mxgraph/typed-mxgraph/blob/v1.0.8/lib/view/mxGraph.d.ts#L2883)

In maxGraph, the signature of Graph.getLabel has been simplified, probably by mistake during the migration

maxGraph/packages/core/src/view/mixins/LabelMixin.type.ts

Line 74 in c4b3590

getLabel: (cell: Cell) => string | null;

[tbouffard]

I have seen the same problem in the OrgChart story, see #532