Add favicon

I used the logo image on the site to generate a favicon using
[Real
Favicon Generator tool](http://realfavicongenerator.net/).

Author: Petru-Vasile Avram

docs/_includes/head.html

@@ -2,6 +2,18 @@
 <meta http-equiv="X-UA-Compatible" content="IE=edge">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 
+<link rel="apple-touch-icon" sizes="57x57" href="/images/apple-touch-icon-57x57.png?v=699Nxpjr2A">
+<link rel="apple-touch-icon" sizes="60x60" href="/images/apple-touch-icon-60x60.png?v=699Nxpjr2A">
+<link rel="apple-touch-icon" sizes="72x72" href="/images/apple-touch-icon-72x72.png?v=699Nxpjr2A">
+<link rel="icon" type="image/png" href="/images/favicon-32x32.png?v=699Nxpjr2A" sizes="32x32">
+<link rel="icon" type="image/png" href="/images/favicon-16x16.png?v=699Nxpjr2A" sizes="16x16">
+<link rel="manifest" href="/images/manifest.json?v=699Nxpjr2A">
+<link rel="mask-icon" href="/images/safari-pinned-tab.svg?v=699Nxpjr2A" color="#F6F6F6">
+<link rel="shortcut icon" href="/images/favicon.ico?v=699Nxpjr2A">
+<meta name="msapplication-TileColor" content="#da532c">
+<meta name="msapplication-config" content="/browserconfig.xml?v=699Nxpjr2A">
+<meta name="theme-color" content="#f6f6f6">
+
 <title>
   {{ page.title }}
 </title>

docs/browserconfig.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<browserconfig>
+  <msapplication>
+    <tile>
+      <square70x70logo src="/images/mstile-70x70.png?v=699Nxpjr2A"/>
+      <square150x150logo src="/images/mstile-150x150.png?v=699Nxpjr2A"/>
+      <wide310x150logo src="/images/mstile-310x150.png?v=699Nxpjr2A"/>
+      <TileColor>#da532c</TileColor>
+    </tile>
+  </msapplication>
+</browserconfig>