deno support?

**Is your feature request related to a problem? Please describe.**
I have created a called [ffmpeg-templates](https://github.com/andykais/ffmpeg-templates) in [deno](https://deno.land) which uses ffmpeg on the command line.

**Describe the solution you'd like**
It would be fantastic if I could bundle ffmpeg into this library rather than asking users to install an external dependency

**Describe alternatives you've considered**
The current implementation is the alternative, use the system's ffmpeg and ask developers to install it.

**Additional context**
Deno strives for parity with browsers, including webassembly support https://deno.land/manual@v1.5.2/getting_started/webassembly.

[denoify](https://www.npmjs.com/package/denoify) is a package that assists in porting npm modules to deno