docs: add Interactive region annotation card to gallery (#689)

Author: timtreis

docs/_static/gallery/interactive_annotate.png

@@ -52,6 +52,15 @@ Render H&E tissue, overlay spots, color by gene expression and by cluster,
 and finish with a publication-style figure.
 :::
 
+:::{grid-item-card} Interactive region annotation
+:link: notebooks/examples/interactive_annotate
+:link-type: doc
+:img-top: _static/gallery/interactive_annotate.png
+
+Draw regions of interest directly on a `spatialdata-plot` canvas with
+`sdata.pl.annotate(...)` and persist them as a `ShapesModel` element.
+:::
+
 ::::
 
 ```{toctree}