Does Apple have a distribution platform for web apps? I have built a web app that I want to distribute to Mac users (using Safari on OS X). What's the best way to do that?

Google, for example, has Chrome Hosted Apps and Chrome Packaged Apps (for web apps, not mobile) that can be distributed through the Google Play.

Best I can tell, (Apple) App Store only contains mobile apps for iOS. And all the OS X apps seem to be developed by Apple only? And not by any third party developers.

Chrome Hosted Apps, as an example in contrast, makes the process simple. All you have to do is create a JSON file with some meta data about the app and upload the app to Google Play. Then the download is just a simple link to the URL of your web app. Done. I'm looking for something similar from Apple. Or are they just out of the web app game?
Apple does not have a dedicated web app store or platform. Apple's iOS App Store and the Mac App Store both require an app bundle be submitted.

It is possible to wrap up a locally hosted web site as an application. A minimal amount of code is required for this approach. This can then be submitted to Apple for review and possible inclusion.

See results for the search wrap web site in ios app webview for possible implementation approaches.