feat: implement og protocol meta tags

Author: ludgie

src/template_pre.html

@@ -5,6 +5,13 @@
 <meta charset="utf-8" />
 <meta name="description" content="labwc"/>
 <meta name="viewport" content="width=device-width">
+<link rel="icon" type="image/png" href="img/labwc.png">
+<!-- Open Graph protocol -->
+<meta property="og:title" content="labwc" />
+<meta property="og:type" content="website" />
+<meta property="og:image" content="img/labwc2-with-text.png" />
+<meta property="og:url" content="https://labwc.github.io" />
+<meta property="og:description" content="labwc" />
 <style>
 body {
 	overflow-y: scroll;