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.Roman = true;
  t["Rotis Serif"] = true;
  t.Sabon = true;
  t.Scala = true;
  t.Seagull = true;
  t.Sistina = true;
  t.Souvenir = true;
  t.STIX = true;
  t["Stone Informal"] = true;
  t["Stone Serif"] = true;
  t.Sylfaen = true;
  t.Times = true;
  t.Trajan = true;
  t["Trinité"] = true;
  t["Trump Mediaeval"] = true;
  t.Utopia = true;
  t["Vale Type"] = true;
  t["Bitstream Vera"] = true;
  t["Vera Serif"] = true;
  t.Versailles = true;
  t.Wanted = true;
  t.Weiss = true;
  t["Wide Latin"] = true;
  t.Windsor = true;
  t.XITS = true;
});
const getSymbolsFonts = getLookupTableFactory(function (t) {
  t.Dingbats = true;
  t.Symbol = true;
  t.ZapfDingbats = true;