add <link rel="canonical">

language_checklist.html

@@ -4,6 +4,7 @@
 <title>Programming Language Checklist</title>
 <link rel="shortcut icon" type="image/png" href="/favicon.ico"/>
 <meta name="viewport" content="width=device-width, initial-scale=1">
+<link rel="canonical" href="https://www.mcmillen.dev/language_checklist.html">
 <style>
 body {
   font-size: 16px;