Include image blur hash in api requests

[jwr1]

At the moment, the image object sent in API requests provides the following keys: filePath, sourceUrl, storageUrl, altText, width, and height. Though, the database contains an additional blur_hash value, which is pretty much a small blurred image preview in the representation of text (good for showing before the actual image finishes loading). It would be nice if this value were included in the API.