Pinch zoom gesture does not work on touchscreen

[Esokrates]

Attach (recommended) or Link to PDF file here:

Configuration:

• Web browser and its version: Firefox 88
• Operating system and its version: Ubuntu 21.04
• PDF.js version: 2.8.243
• Is a browser extension: No

Steps to reproduce the problem:

1. Open a pdf in Firefox on a touchscreen device
2. Try to zoom using the pinch gesture

What is the expected behavior?

Pinch zoom works.

What went wrong?

Pinch zoom does not work.

Related bugs reports on the firefox bugzilla:

https://bugzilla.mozilla.org/show_bug.cgi?id=1677933
https://bugzilla.mozilla.org/show_bug.cgi?id=1659492

[Snuffleupagus]

Related bugs reports on the firefox bugzilla:

https://bugzilla.mozilla.org/show_bug.cgi?id=1677933
https://bugzilla.mozilla.org/show_bug.cgi?id=1659492

Duplicate of #2582 (for all intents and purposes); please also note that it's generally not necessary to "re-file" issues from Bugzilla here at GitHub.