table-plugin: Insert new table column left and row above

[Raigen]

I am currently implementing the table plugin for our new plate-based editor. In our concept we want to give the user the option to add a new column left and right of the currenct selection. Same for a row above and below. This does work for most parts, but if I want to add a new column left of the very first column, I run into an error.
The current insertTableColumn and insertTableRow functions are using Path.next and require a valid path. But from the first column/row there is no valid previous path anymore.
It works to add new elements at the current path instead of .next. But For columns that is a rather big function to clone it and keep it in sync with changes, just for replacing the at option.

Is there a way to archive what we want with the current set of functions and I just did not found it?
Changing the behavior in general would be a breaking change. So some sort of option is probably the easierst solution. For example a path transform with a default Path.next for backwards compatability. Or a basic 'current' | 'next' string option.
Is this something you would accept a pull request about?

[zbeyens]

PR's welcome, at option would be great to override the default behavior