Add Pdf.ContainsJavaScript for detecting embedded JavaScript in PDFs

[Copilot]

No .NET API existed to detect embedded JavaScript in PDF files — a common security requirement for file upload validation. The CLI equivalent is qpdf --json file.pdf | grep -i javascript.

Changes

• QPdfNet/Info/Pdf.cs — Adds ContainsJavaScript(string fileName) static method: runs qpdf's JSON output pipeline and performs a case-insensitive search for "javascript" in the result, mirroring the CLI grep approach
• QpdfNetTest/TestFiles/withjavascript.pdf — Minimal valid PDF containing a /S /JavaScript action object, used as test fixture
• QpdfNetTest/QpdfTests.cs — Adds TestContainsJavaScript and TestContainsNoJavaScript test cases

Usage

if (Pdf.ContainsJavaScript(uploadedFilePath))
{
    // reject or quarantine the file
}

Original prompt

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This section details on the original issue you should resolve

<issue_title>Detect JavaScript in a PDF</issue_title>
<issue_description>Hi,

I want to implement security in our application for upload files. My requirement is to detect if there're any javascripts in pdf file. I was wondering if QPdfNet has any function for this.

With command line tool we can use

qpdf –json yourfile.pdf | grep -i javascript</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Detect JavaScript in a PDF #22

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