docs: public static void reloadData(IAsyncHandler<Void> doneHandler) {
          synchronized(URILoadingRegistry.class) {
              if (instance == null) {
                  doneHandler.handle((Void) null);
                  return;
              }
              Map<URILoadingRegistry, IAsyncResultHandler<Void>> regs = instance.handlers;
              Vertx vertx = instance.vertx;
              URI uri = instance.uri;
              Map<String, String> config = instance.config;
              AtomicInteger ctr = new AtomicInteger(regs.size());
              OneShotURILoader newLoader = new OneShotURILoader(vertx, uri, config);
  
              regs.entrySet().stream().forEach(pair -> {
                  // Clear the registrys' internal maps to prepare for reload.
                  // NB: If we add production hot reloading, we'll need to work around this (e.g. clone?).
                  pair.getKey().getMap().clear();
                  // Re-subscribe the registry.
                  newLoader.subscribe(pair.getKey(), result -> {
                      checkAndFlip(ctr.decrementAndGet(), newLoader, doneHandler);
                  });
              });
              checkAndFlip(ctr.get(), newLoader, doneHandler);
          }
      }