message: app: fix incorrect crate name in README.md
  The crate name should be nydus-app.
diff: -# nydus-error
  +# nydus-app
  The `nydus-app` crate is a collection of utilities to help creating applications for [`Nydus Image Service`](https://github.com/dragonflyoss/image-service) project, which provides:
  - `struct BuildTimeInfo`: application build and version information.
  @@ -23,7 +23,7 @@ Add `nydus-app` as a dependency in `Cargo.toml`
  nydus-app = "*"
  ```
  -Then add `extern crate nydus-error;` to your crate root if needed.
  +Then add `extern crate nydus-app;` to your crate root if needed.
  ## Examples
  