Addresses mikecao/umami#460

Adds an explicit meta tag for the viewport, resizes the navigation link size
for smaller screens

components/layout/Header.module.css

@@ -44,4 +44,7 @@
   .header {
     padding: 0 15px;
   }
+  .nav {
+    font-size: var(--font-size-normal);
+  }
 }

pages/_app.js

@@ -36,6 +36,7 @@ export default function App({ Component, pageProps }) {
         <link rel="mask-icon" href="safari-pinned-tab.svg" color="#5bbad5" />
         <meta name="msapplication-TileColor" content="#da532c" />
         <meta name="theme-color" content="#ffffff" />
+        <meta name="viewport" content="width=device-width, initial-scale=1" />
       </Head>
       <Intl>
         <Component {...pageProps} />