Add tables to extended objects

Extended objects have properties and functionality that exceed the capabilities of a standard `Object`. An implemented example is a list. Adding more extended objects is crucial to enable specific diagram types.

Tables in particular are useful in a variety of digrams.


You can find `extended objects` [here.](https://github.com/MerrimanInd/drawpyo/blob/main/src/drawpyo/diagram/extended_objects.py)

Start in src/drawpyo/diagram/extended_objects.py and inspect the existing list implementation. Use the linked example and repository conventions to determine the table object's required behavior; no test file is named, so completion should be checked against the existing extended-object behavior.

Written by the indexing model from the issue text.