Thumbnail and file accept any file type

[jkevingutierrez]

Found a bug? Please fill out the sections below. 👍

Issue Summary

When you are uploading a Video or Audio file, you are able to upload any kind of file. You could even upload a video as audio.

It would be good to limit the file type, to only accept video and audio files

Steps to Reproduce

1. Start a new project with wagtail start myproject
2. Integrate wagtailmedia
3. Go to the media page (/admin/media/)
4. Click on Add Audio or Add Video.
5. Try to upload any non-media file (pdf, doc, etc)

Any other relevant information. For example, why do you consider this a bug and what did you expect to happen instead?

You shouldn't be able to upload non-media files or upload a video in the audio tab or vice versa.

Technical details

• Python version: 3.8.5
• Django version: 3.0.10
• Wagtail version: 2.10.1
• wagtailmedia: 0.6.0
• Browser version: Chrome 85

[zerolab]

Hey @jkevingutierrez, I've opened #140 to fix this.
Would be great if you could help test it.