Web Inspector: should be able to type new line in Text node

[Sam Sneddon [:gsnedders]]

When editing a Text node in the DOM, under the Elements tab, it should be possible to add a new line character to the Text node. I would expect Shift+Enter would do this.

[Radar WebKit Bug Importer]

<rdar://problem/77336609>

[Joseph Pecoraro]

Looks like:

```
    _startEditingTextNode(textNode)
    {
        if (WI.isBeingEdited(textNode))
            return true;

        var config = new WI.EditingConfig(this._textNodeEditingCommitted.bind(this), this._editingCancelled.bind(this));
        config.spellcheck = true;
        this._editing = WI.startEditing(textNode, config);
        window.getSelection().setBaseAndExtent(textNode, 0, textNode, 1);

        return true;
    }
```

Maybe this just needs `config.multiline = true`.