Adding Facebook image sharing height and width.

Providing these options ensures that the share image is immediately rendered in preview every time, without it the first time there will be no image preview until Facebook has crawled the site once.

README.md

@@ -199,6 +199,8 @@ Minimum required xml markup for the browserconfig.xml file is as follows:
 
 * [ ] **Facebook Open Graph:** ![Low][low_img] All Facebook Open Graph (OG) are tested and no one is missing or with a false information. Images need to be at least 600 x 315 pixels, 1200 x 630 pixels recommended.
 
+* [ ] **Facebook Image Preview; use og:image:width and og:image:height** ![Low][low_img] Using these tags will specify the image dimensions to the crawler so that it can render the image immediately without having to asynchronously download and process it.
+
 ```html
 <meta property="og:type" content="website">
 <meta property="og:url" content="https://example.com/page.html">
@@ -207,9 +209,12 @@ Minimum required xml markup for the browserconfig.xml file is as follows:
 <meta property="og:description" content="Description Here">
 <meta property="og:site_name" content="Site Name">
 <meta property="og:locale" content="en_US">
+<meta property="og:image:width" content="1200">
+<meta property="og:image:height" content="630">
 ```
 
 > * 📖 [A Guide to Sharing for Webmasters](https://developers.facebook.com/docs/sharing/webmasters/)
+> * 📖 [Best Practices - Sharing](https://developers.facebook.com/docs/sharing/best-practices/)
 > * 🛠 Test your page with the [Facebook OG testing](https://developers.facebook.com/tools/debug/)
 
 * [ ] **Twitter Card:** ![Low][low_img]