Profile picture processing

This is still single-threaded, so perf is pretty bad. Will need to think
about how to do this more efficiently in a web context where we don't
have threading.

src/result.rs

@@ -1,3 +1,3 @@
 use crate::error::Error;
 
-type Result<T> = std::result::Result<T, Error>;
+pub type Result<T> = std::result::Result<T, Error>;