Simple PWA HTML tags.
If you don't need the fancy features of a service worker and just want your SPA to behave nicely when a user adds to homescreen, or creates a desktop Chrome shortcut, these are the bare minimum HTML tags needed (not including the title, charset and other usual tags you would also have.)
Description and Image tags are useful for sharing purposes.
<meta name="viewport" content="initial-scale=1, width=device-width"/>
<meta name="mobile-web-app-capable" content="yes"/>
<meta name="apple-mobile-web-app-capable" content="yes"/>
<meta name="theme-color" content="#000000"/>
<meta name="apple-mobile-web-app-status-bar-style" content="black"/>
<meta property="og:title" content="MyApp"/>
<meta property="og:description" content="This is my app"/>
<meta property="og:image" content="img/hero.png"/>
<link rel="icon" sizes="192x192" href="img/icon.png"/>
<link rel="apple-touch-icon" sizes="192x192" href="img/icon.png"/>