web frontend for ffmpeg.wasm

I wanted to help someone, with generating a video from images. Since cli tools can be complicated to explain, I found ffmpeg.wasm and wanted to turn that into a web tool.

It features a couple more specialized tools, like rendering images into a video and getting a poster image from a video. And a more generic video compression tool. But you can also directly edit the generated ffmpeg commands.

Some notes on ffmpeg.wasm, given that it's webassembly, afaik it has a 2gb file size limit (which I think should be fine for the media you'd want to use it for), and it's a lot slower than running natively with the cli. But it means you can use it wherever you have a browser.

The ui is based on the custom one for the spritesheet tool, but improved, and with more types of input. I want to keep improved the inputs as I make more things.