Implement decryption in Javascript directly in README

[pcrockett]

Because libsodium has Javascript bindings, we could theoretically implement decryption directly in the README.html file that goes with backup packages. This would:

1. Eliminate the need to have separate native decrypt binaries for all platforms
2. Give backup holders a MUCH more friendly UI

It would completely eliminate the need for #13 #14 and #15 (which are closed now).

Thinking it would be good to have a readme.html as it is now, but also a decrypt.html. The readme could link to the decrypt. Javascript, CSS, and other resources could be saved in the hidden .kin folder.

• [ ] Look at using WebAssembly for heavy-lifting and code-sharing purposes
• [ ] Figure out a location to build the web app
• [ ] Create build script that builds both web app and the Rust project (could potentially use Rust's built-in build.rs functionality)

[pcrockett]

Did a little research, and there doesn't seem to be a way to get a Javascript web app to stream large amounts of data to a file on the local file system. You can write blobs of data using data URIs, but data URIs have a maximum size. So this idea wouldn't work if the user had, say, 10 GB of data to decrypt.

So it looks like our options are:

1. Severely restrict the amount of "private" data a user can back up
2. Use native applications rather than Javascript

Fooey.