pdf not support to show Khmer characters

[BoyPhanna]

Describe the bug
When i use pdf package to generate pdf for Khmer language characters it show incorrect.
This is result out put from generate pdf.
សួ​ស្​ដី

To Reproduce

Future generatePdf() async {
final font = await PdfGoogleFonts.khmerRegular();
final pdf = pw.Document();

String arabicText = 'សួស្ដី';

// Convert logical Arabic text to visual order
String visualText = logicalToVisual(arabicText);

pdf.addPage(
pw.Page(
build: (pw.Context context) {
return pw.Center(
child: pw.Column(children: [
pw.Text(
visualText,
style: pw.TextStyle(fontSize: 24, fontFallback: [font]),
),
]));
},
),
);

// Save or print the PDF
final outputFile = File('path_to_output.pdf');
await outputFile.writeAsBytes(await pdf.save());
}

**Screenshots**
![pdf](https://github.com/user-attachments/assets/61e42bc0-dd98-4880-9704-a79bc91f37c4)

**Desktop (please complete the following information):**
 - [ ] iOS
 - [ ] Android
 - [ ] Browser
 - [ ] Windows
 - [ ] Linux

**Smartphone (please complete the following information):**
 - Device: [e.g. iPhone6]
 - OS: [e.g. iOS8.1]
 - Browser [e.g. stock browser, safari]
 - Version [e.g. 22]

**Additional context**