Add attribution to image block

[simison]

What problem does this address?

In State Of The Word 2022 we saw Openverse introduced, and how attribution was copied from Openverse to the editor (video at 7min):

In the example, they used paragraph blocks.

Plugins extending WordPress might pull from other image sources as well, and place attribution in caption field:

What is your proposed solution?

It could be useful to have "attribution" or a similar field in image block attributes.

Theme or site could style the attribution differently from the caption; often it's just after the caption text, but in a slightly smaller or thinner style. Other times it's over the image in a much smaller copy while the caption is under the image.

Attribution text is also useful when added to image tag e.g. via schema attributes like license, creditText, or creator.

Adding this to image block would propagate the feature to other blocks such as Gallery.

Some examples from various news sites:

There could be some other uses in different layout situations, for example New York Times:

[Mamaduka]

I think this might be easier if we start using inner blocks for citation, and then we can have separate inner blocks for attributions—related PR #31823.