fix(smithereens): call the worker's loading function

Javascript is a revolting mess of a language, and those two brackets are
all that was missing to run that code... With that being said, there
seems to be another issue with loading the JSON — but now at least we're
seeing those errors!

web/src/lib/smithereens.ts

@@ -23,7 +23,7 @@ const smithereens: Smithereens = { ...defaultSmithereens };
             }
         })
     })
-});
+})();
 
 // What type should 'proxy' be?
 function postResult(proxy: undefined) {