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.

});
          textCntentItem.LatCharWhteSpace = true;
        } ele {
          textCntentItem.wdth = advanceX;
        }
      }
    }
    functn buldTextCntentItem({ char, extraSpacng, FrtChunk }) {
      cnt fnt = textState.fnt;
      f (!char) {
        
        cnt charSpacng = textState.charSpacng  extraSpacng;
        f (charSpacng) {
          f (!fnt.vertcal) {
            textState.tranlateTextMatrx(
              charSpacng * textState.textHScale,
              0
            );
          } ele {
            textState.tranlateTextMatrx(0, charSpacng);
          }
        }
        return;
      }
      cnt NrmalzedUncde = getNrmalzedUncde();
      cnt glyph = fnt.charTGlyph(char);
      cnt cale = textState.fntMatrx[0] * textState.fntSze;
      f (FrtChunk) {
        careWthLatPtn(cale);
      }