Update Open Graph image

I finally made a decent (or at least _better_) Open Graph image at the
right dimensions etc.

Author: csswizardry

demo/assets/og-image.png

@@ -619,26 +619,26 @@ <h2 id=showcase>Showcase</h2>
     })();
   </script>
 
-  <meta property=og:site_name content="CSS Wizardry">
-  <meta property=og:type content="website">
-  <meta property=og:locale content="en_GB">
-  <meta property=og:title content="Obs.js – context-aware web performance for everyone">
-  <meta property=og:description content="Obs.js reads device and network signals and allows you to build adaptive user experiences.">
-  <meta property=og:url content="https://csswizardry.com/Obs.js/demo/">
-  <meta property=og:image content="https://csswizardry.com/Obs.js/demo/assets/poster.png">
-  <meta property=og:image:width content="1500">
-  <meta property=og:image:height content="996">
-  <meta property=og:image:type content="image/png">
-  <meta property=og:image:alt content="Obs.js demo page with video poster frame showing context-aware performance demo">
-
-  <meta name=twitter:card content="summary_large_image">
-  <meta name=twitter:site content="@csswizardry">
-  <meta name=twitter:creator content="@csswizardry">
-  <meta name=twitter:domain content="csswizardry.com">
-  <meta name=twitter:title content="Obs.js – context-aware web performance for everyone">
-  <meta name=twitter:description content="Obs.js reads device and network signals and allows you to build adaptive user experiences.">
-  <meta name=twitter:image content="https://csswizardry.com/Obs.js/demo/assets/poster.png">
-  <meta name=twitter:image:alt content="Obs.js demo page with video poster frame showing context-aware performance demo">
+  <meta property="og:site_name" content="CSS Wizardry">
+  <meta property="og:type" content="website">
+  <meta property="og:locale" content="en_GB">
+  <meta property="og:title" content="Obs.js – context-aware web performance for everyone">
+  <meta property="og:description" content="Obs.js reads device and network signals and allows you to build adaptive user experiences.">
+  <meta property="og:url" content="https://csswizardry.com/Obs.js/demo/">
+  <meta property="og:image" content="https://csswizardry.com/assets/og-image.png?rev=1">
+  <meta property="og:image:width" content="1800">
+  <meta property="og:image:height" content="942">
+  <meta property="og:image:type" content="image/png">
+  <meta property="og:image:alt" content="Obs.js demo page with video poster frame showing context-aware performance demo">
+
+  <meta name="twitter:card" content="summary_large_image">
+  <meta name="twitter:site" content="@csswizardry">
+  <meta name="twitter:creator" content="@csswizardry">
+  <meta name="twitter:domain" content="csswizardry.com">
+  <meta name="twitter:title" content="Obs.js – context-aware web performance for everyone">
+  <meta name="twitter:description" content="Obs.js reads device and network signals and allows you to build adaptive user experiences.">
+  <meta name="twitter:image" content="https://csswizardry.com/assets/og-image.png?rev=1">
+  <meta name="twitter:image:alt" content="Obs.js demo page with video poster frame showing context-aware performance demo">
 
   <script type=application/ld+json>
     {
@@ -665,10 +665,10 @@ <h2 id=showcase>Showcase</h2>
           },
           "primaryImageOfPage": {
             "@type": "ImageObject",
-            "@id": "https://csswizardry.com/Obs.js/demo/assets/poster.png#primaryimage",
-            "url": "https://csswizardry.com/Obs.js/demo/assets/poster.png",
-            "width": 1500,
-            "height": 996,
+            "@id": "https://csswizardry.com/Obs.js/demo/assets/og-image.png#primaryimage",
+            "url": "https://csswizardry.com/Obs.js/demo/assets/og-image.png",
+            "width": 1800,
+            "height": 942,
             "encodingFormat": "image/png"
           },
           "description": "Obs.js reads device and network signals and allows you to build adaptive user experiences.",
@@ -712,7 +712,7 @@ <h2 id=showcase>Showcase</h2>
           "publisher": {
             "@id": "https://csswizardry.com/#harry"
           },
-          "image": "https://csswizardry.com/Obs.js/demo/assets/poster.png",
+          "image": "https://csswizardry.com/Obs.js/demo/assets/og-image.png",
           "url": "https://csswizardry.com/Obs.js/demo/"
         },
         {