Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
const fontHeight = Math.hypot(tx[2], tx[3]);
  const fontAscent = fontHeight * getAscent(style.fontFamily, ctx);
  let left, top;
  if (angle === 0) {
    left = tx[4];
    top = tx[5] - fontAscent;
  } else {
    left = tx[4] + fontAscent * Math.sin(angle);
    top = tx[5] - fontAscent * Math.cos(angle);
  }
  
  
  textDiv.style.left = `${left}px`;
  textDiv.style.top = `${top}px`;
  textDiv.style.fontSize = `${fontHeight}px`;
  textDiv.style.fontFamily = style.fontFamily;
  
  textDiv.setAttribute("role", "presentation");
  textDiv.textContent = geom.str;
  
  textDiv.dir = geom.dir;
  
  
  if (task._fontInspectorEnabled) {
    textDiv.dataset.fontName = geom.fontName;
  }
  if (angle !== 0) {
    textDivProperties.angle = angle * (180 / Math.PI);
  }