Include name property in outputs of page.images

[djr2015]

When working with images inside pdfs, how about also recording the object's id when computing page.images via:
attr["name"]=obj.name
here: https://github.com/jsvine/pdfplumber/blob/stable/pdfplumber/page.py#L369

Doing this enables mapping images' coordinates and dimensions to their identifiers as recorded in the pdf (e.g. /Im0) which is useful for downstream tasks involving other pdf parsing libraries.

[jsvine]

Thanks! That's a relatively straightforward add, now available on develop and will be merged into the next release: 6ef62c9