Add theme-color and twitter:card meta tags

Author: bikeshedder

theme/head.hbs

@@ -1,5 +1,7 @@
 <meta property="og:site_name" content="{{ book_title }} - Contract-First API System">
 <meta property="og:title" content="{{ chapter_title }}">
-<meta property="og:type" content="photo">
-<meta property="og:image" content="https://webwire.dev/teaser.png">
+<meta property="og:type" content="article">
+<meta property="og:image" content="https://webwire.dev/og-image.png">
 <meta property="og:description" content="{{ description }}">
+<meta name="theme-color" content="#2c89a0">
+<meta name="twitter:card" content="summary_large_image">