fix validation

.htmlvalidate.json

@@ -0,0 +1,6 @@
+{
+  "extends": ["html-validate:recommended"],
+  "rules": {
+    "no-trailing-whitespace": "off"
+  }
+}

src/_includes/layouts/base.njk

@@ -1,4 +1,4 @@
-<!doctype html>
+<!DOCTYPE html>
 <html lang="{{ site.language }}">
 <head>
   <meta charset="utf-8">