Annotated images block

[SeanDS]

A block that lets you make links/text on top of images. Good for showing e.g. a lab layout with links to relevant logbook pages/posts, but also for drawing on top of graphs to mark features.

Ideally this would subclass the image block to avoid having to duplicate and maintain the features it provides.

[SeanDS]

Feature suggestion: image block without caption hovering over the top of the bottom of the figure. Especially bad for figures with x-axes near the bottom. Make a figure block?