Allow viewing Flash posts with the Ruffle emulator.
Known issues:
* Many flash files aren't fully supported.
* In development it sometimes spazzes out and starts triggering random
keyboard shortcuts when you press any key. This doesn't happen with
the browser extension.
* We have to put the .wasm file in the public/packs/js directory because
Ruffle is hardcoded to search for it there.
* If you're running Nginx, you need to make sure you're serving the
right MIME type for .wasm files or it won't work.
* We're using Some Random Guy's unofficial NPM package for Ruffle, since the
Ruffle project doesn't publish an official package themselves. We
should build our own package.
References:
* https://github.com/ruffle-rs/ruffle
* https://github.com/ruffle-rs/ruffle/wiki/Using-Ruffle#configure-webassembly-mime-type
* https://www.npmjs.com/package/ruffle-mirror
