Add Open Graph metadata

We cannot use relative paths for the image [1] so we are using the logo
in GitHub

[1]: https://stackoverflow.com/questions/9858577/open-graph-can-resolve-relative-url

packages/cli/templates/form-trigger.handlebars

@@ -3,6 +3,10 @@
 		<meta charset='UTF-8' />
 		<meta name='viewport' content='width=device-width, initial-scale=1.0' />
 		<meta name="description" content="{{formDescriptionMetadata}}" />
+		<meta property="og:title" content="n8n Form: {{formTitle}}" />
+		<meta property="og:description" content="{{formDescriptionMetadata}}" />
+		<meta property="og:type" content="website" />
+		<meta property="og:image" content="https://github.com/n8n-io/n8n/blob/master/assets/n8n-logo.png?raw=true" />
 		<link rel='icon' type='image/png' href='https://n8n.io/favicon.ico' />
 		<link
 			href='https://fonts.googleapis.com/css?family=Open+Sans'