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.
describe("Page", function () {
    let pdfLoadingTask, pdfDocument, page;
    beforeAll(async function () {
      pdfLoadingTask = getDocument(basicApiGetDocumentParams);
      pdfDocument = await pdfLoadingTask.promise;
      page = await pdfDocument.getPage(1);
    });
    afterAll(async function () {
      await pdfLoadingTask.destroy();
    });
    it("gets page number", function () {
      expect(page.pageNumber).toEqual(1);
    });
    it("gets rotate", function () {
      expect(page.rotate).toEqual(0);
    });
    it("gets ref", function () {
      expect(page.ref).toEqual({ num: 15, gen: 0 });
    });
    it("gets userUnit", function () {
      expect(page.userUnit).toEqual(1.0);
    });
    it("gets view", function () {
      expect(page.view).toEqual([0, 0, 595.28, 841.89]);
    });
    it("gets view, with empty/invalid bounding boxes", async function () {
      const viewLoadingTask = getDocument(
        buildGetDocumentParams("boundingBox_invalid.pdf")
      );
      const pdfDoc = await viewLoadingTask.promise;