Trailing spaces disappear on Firefox

[garrettn]

Example: https://stackblitz.com/edit/react-sk9ruu

The example was based on #28, but the config value seems to have nothing to do with it. I also saw some related discussion in #19 but there hasn't been any movement on that.

In FF, if you leave a space after a word and stop, the space disappears after a short time. In Chromium, the space gets replaced with a   and thus doesn't disappear visually.

Tested in FF 62 on Ubuntu 18.04.

Edit: I suspected it might be a bug with TinyMCE itself, but in this minimal example with the latest version, I couldn't reproduce the issue.