Converted file does not play in Mac Finder and QuickTime media player

**Describe the bug**
While trying to create BT.2020 H.264 files with ffmpeg.wasm I ran into a case where the conversion succeeds, but the resulting file only has a thumbnail and doesn't actually play in media players.

**To Reproduce**

1. Load demo file
2. Paste the conversion commands below
3. Transcode
4. Download the result and try to play it
5. Note in Mac Finder it will only display a thumbnail and not actually play. In Chrome it does play.
6. Compare with this file: https://www.wide-gamut.com/assets/video-hdr/P3-GREEN-HDR-1000nits.mp4 which will play in HDR mode in Mac Finder.

```
[
"-i",
"video.webm",
"-vf", "format=yuv420p10le",
"-c:v", "libx264",
"-preset", "slow",
"-crf", "18",
"-color_primaries", "bt2020",
"-colorspace", "bt2020nc",
"-color_trc", "smpte2084",
"video.mp4"
]
```
**Expected behavior**
Converted file plays in Mac Finder as well as in the browser

**Screenshots**

_File does not have play button – it does play in a browser though!_

_File has play button and plays in Finder_

**Desktop (please complete the following information):**
- OS: Mac OS
- Browser Chrome latest

**Additional context**
Workflow related to #762