How To Make A Web App Shortcut In Firefox:
Step 1: Bookmark Your Page In Firefox (The Star In The Navigation Toolbar)
Step 2: Open your bookmark library.
Step 3: Drag the bookmark to your applications folder (or programs folder on windows).
Step 4: Open your applications folder (or programs folder on windows) and click on it to launch it. It may end with the extension ".webloc" on mac. It might be different on windows.
Step 5: It will launch in a new tab (or window) and you will be all set.