add GSC

Author: ryosukeeeeee

docs/index.html

@@ -63,6 +63,11 @@
       rel="stylesheet"
       href="//cdn.jsdelivr.net/npm/gitalk/dist/gitalk.css"
     />
+    <!-- GSC -->
+    <meta
+      name="google-site-verification"
+      content="I9AUrsDVI86dZZUEJ2wSX4torsBJsq0bihBPHd_Efx4"
+    />
     <style>
       .sidebar {
         padding: 0 0 0 0;