[@types/pdfmake] extended background definition for other content types (#35323)
[@types/pdfmake] extended background definition for other content types (#35323)

* extended background definition for other content types

* make background type definition more readable

Co-Authored-By: Dan Rumney <74e3538a67832cb070a011d9dbab5d4adfd57b0f@gmail.com>

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