Adds an entry to the
pipelineData object belonging to this Game Object.
If the 'key' already exists, its value is updated. If it doesn't exist, it is created.
value is undefined, and
key is removed from the data object.
Both the pipeline and post pipelines share the pipeline data object together.
The key of the pipeline data to set, update, or delete.
The value to be set with the key. If
This Game Object instance.