Check added that an Extension is a direct object

[samalloing]

Hi @carlwilson

Added an extra check that an extension is a direct object. This is based on the Arlington PDF model: https://github.com/pdf-association/arlington-pdf-model/blob/master/tsv/latest/Extensions.tsv
As test file you can use https://github.com/qpdf/qpdf/blob/main/qpdf/qtest/qpdf/extensions-adbe-other.pdf

Sam

[codecov]

Codecov Report

Base: 46.22% // Head: 46.22% // No change to project coverage 👍

Coverage data is based on head (a7e8dff) compared to base (6f8bc2a).
Patch has no changes to coverable lines.

Additional details and impacted files

@@              Coverage Diff               @@
##             integration     #780   +/-   ##
==============================================
  Coverage          46.22%   46.22%           
  Complexity          1056     1056           
==============================================
  Files                 57       57           
  Lines               9057     9057           
  Branches            1607     1607           
==============================================
  Hits                4187     4187           
  Misses              4330     4330           
  Partials             540      540           

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