feat: Enable PreferCSSPageSize option for PDF generation

[filzrev]

This PR intended to fix #9842.

By default, docfx generating PDF files with following settings.

• PageSize: Letter (215.9 x 279.4)
• PageOrientation: Portrait

This PR enable PagePdfOptions's PreferCSSPageSize settings.
So It can customize PDF option by custom CSS.

Example CSS settings

@media print {
  @page {
    size: A4 landscape
  }
}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.98%. Comparing base (fe673ec) to head (5bc535b).
Report is 113 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9850      +/-   ##
==========================================
+ Coverage   74.31%   78.98%   +4.66%     
==========================================
  Files         536      538       +2     
  Lines       23189    23323     +134     
  Branches     4056     4049       -7     
==========================================
+ Hits        17234    18421    +1187     
+ Misses       4853     3774    -1079     
- Partials     1102     1128      +26     

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[yufeih]

Thank you @filzrev !