assets: conditionally load format assest #72
Description
What problem does this address?
Some formats need additional assets that currently load on every post/page, even if the format is not used.
Proposed solution
Conditionally load additional assets if formats is in use.
Additional context
Currently, there is no core API or helper to determine this, and it needs a custom helper.
We can introduce hasFormat, which accepts a classname or a tag name or both to evaluate.