Document TrainablePipe.save_activations (#13452)

* Document `TrainablePipe.save_activations`

* Fully qualified links

Co-authored-by: Sofie Van Landeghem <svlandeg@users.noreply.github.com>

* prettier

---------

Co-authored-by: Sofie Van Landeghem <svlandeg@users.noreply.github.com>

website/docs/api/pipe.mdx

@@ -476,6 +476,17 @@ as an attribute to the component's model.
 | ----------- | ---------------------------------------------------------------------------------------------- |
 | **RETURNS** | Whether or not the output dimension of the model can be changed after initialization. ~~bool~~ |
 
+## TrainablePipe.save_activations {id="save_activations",tag="property",version="4"}
+
+Check/set whether this component stores activations. When enabled, the
+activations of the pipe's model are stored in the
+[`Doc.activations`](/api/doc#attributes) dictionary when
+[`set_annotations`](/api/pipe#set_annotations) is called.
+
+| Name        | Description                                                                                                 |
+| ----------- | ----------------------------------------------------------------------------------------------------------- |
+| **RETURNS** | Whether to save activations in the `Doc` object in [`set_annotations`](/api/pipe#set_annotations). ~~bool~~ |
+
 ## TrainablePipe.set_output {id="set_output",tag="method"}
 
 Change the output dimension of the component's model. If the component is not