support zen browser (based on firefox)

[thosil]

Is your feature request related to a problem? Please describe:

It looks like zen browser is not recognized as a compatible browser on stackblitz event if it's a modified firefox.

Describe the solution you'd like:

Just treat it like firefox :-)

Describe alternatives you've considered:

I have no real alternative, but maybe the problem is not a webcontainer-core issue but just a check on stackblitz.com

Additional context:

I follow the "read more about browser support" which leads me to another link pointing on thie repo