feat: add a canonical tag by default

Author: Phosphorus-M

src/theme/index.hbs

@@ -15,6 +15,12 @@
         <!-- Custom HTML head -->
         {{> head}}
 
+        {{#if (eq slug "title-page") }}
+            <link rel="canonical" href="{{ base_url }}/" />
+        {{else}}
+            <link rel="canonical" href="{{ base_url }}/{{ slug }}" />
+        {{/if}}
+
         <meta name="description" content="{{ description }}">
         <meta name="viewport" content="width=device-width, initial-scale=1">
         <meta name="theme-color" content="#ffffff">