Shadow: add shadow in block settings (site editor)

[madhusudhand]

What problem does this address?

Add the shadow component in block settings in the site editor. With current implementation, it is only possible to choose/add shadows to blocks only from the global styles.

Adding shadow in the site editor enables specific blocks to have shadows.

What is your proposed solution?

Proposed UI

Parent issue

#44651

[caseymilne]

That looks good, looking forward to be able to declare it through block/supports.