fix(macos): support app bundle as a framework

[louis-menlo]

Problem

Currently, when bundling a MacOS bundle, tauri-build and tauri-bundle only accept .dylib and .Framework extensions. But there is such case where applications might need to bundle .app in the application Frameworks. See:
https://bitbucket.org/chromiumembedded/cef/wiki/Tutorial.md#markdown-header-mac-os-x-build-steps

Current behavior:

When bundling .app files in Frameworks, it will throw an error stating, "Could not locate framework: {framework}".

Expected behavior:

It should include the .app file in the Frameworks section as soon as developers define it in the tauri config JSON file.

This change merely duplicates the existing .framework logic and also accepts .app files.

if framework.ends_with(".framework") {
   let src_path = PathBuf::from(framework);
   let src_name = src_path
        .file_name()
        .expect("Couldn't get framework filename");
   let dest_path = dest_dir.join(src_name);
   fs_utils::copy_dir(&src_path, &dest_path)?;
   add_framework_sign_path(&src_path, &dest_path, &mut paths);
   continue;
} else if framework.ends_with(".app") {
   let src_path = PathBuf::from(framework);
   if !src_path.exists() {
        return Err(GenericError(format!("Library not found: {framework}")));
      }
   let src_name = src_path.file_name().expect("Couldn't get library filename");
   let dest_path = dest_dir.join(src_name);
   fs_utils::copy_dir(&src_path, &dest_path)?;
      add_framework_sign_path(&src_path, &dest_path, &mut paths);
      continue;
}

Inspiration

We are developing a browser app using Tauri and CEF, a forked version of Tauri-bundle could serve as a temporary solution. However, some developers might install the official version on crates when building the application, so we would like to have this change merged upstream.