Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

t[1005] = 49;
  t[1006] = 50;
  t[1007] = 51;
  t[1008] = 52;
  t[1009] = 53;
  t[1010] = 54;
  t[1011] = 55;
  t[1012] = 56;
  t[1013] = 57;
  t[1081] = 37;
  t[1085] = 43;
  t[1086] = 45;
});
function getStandardFontName(name) {
  const fontName = normalizeFontName(name);
  const stdFontMap = getStdFontMap();
  return stdFontMap[fontName];
}
export {
  getFontNameToFileMap,
  getGlyphMapForStandardFonts,
  getNonStdFontMap,
  getSerifFonts,
  getStandardFontName,
  getStdFontMap,
  getSupplementalGlyphMapForArialBlack,
  getSupplementalGlyphMapForCalibri,
  getSymbolsFonts,
};