Adding a .Pages attribute in PdfWriter to allow setting its MediaBox or Resources fields

[Lucas-C]

This allows for the following usage:

out = PdfWriter()
out.Pages = IndirectPdfDict(
    MediaBox=...,
    Resources=...,
)
out.addpage(page)
out.write(...)

This is a copy of pmaupin#205

[pep8speaks]

Hello @Lucas-C! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file tests/test_examples.py:

Line 112:80: E501 line too long (97 > 79 characters)

• In the file tests/test_roundtrip.py:

Line 94:80: E501 line too long (97 > 79 characters)

Comment last updated at 2021-04-01 13:36:59 UTC