Fixes lint style errors

src/app/__tests__/__snapshots__/App.tsx.snap

@@ -2,7 +2,7 @@
 
 exports[`<App /> renders 1`] = `
 <div
-  className="App"
+  className="app"
 >
   <a
     className="header"

src/app/index.tsx

@@ -15,7 +15,7 @@ interface Route {
 }
 
 const App = ({ route }: Route): JSX.Element => (
-    <div className={styles.App}>
+    <div className={styles.app}>
         <Helmet {...config.APP} />
         <Link to="/" className={styles.header}>
             <img src={logo} alt="Logo" role="presentation" />

src/app/styles.module.scss

@@ -5,21 +5,13 @@ body {
     font-family: "Helvetica-Light", Helvetica, Arial, sans-serif;
 }
 
-.App {
+.app {
     color: $color-white;
 
-    .header {
-        color: inherit;
-        display: block;
-        overflow: auto;
-        padding: 15px;
-        text-decoration: none;
-
-        img {
-            float: left;
-            height: 70px;
-            margin-right: 1em;
-        }
+    img {
+        float: left;
+        height: 70px;
+        margin-right: 1em;
     }
 
     hr {
@@ -28,3 +20,11 @@ body {
         opacity: 0.15;
     }
 }
+
+.header {
+    color: inherit;
+    display: block;
+    overflow: auto;
+    padding: 15px;
+    text-decoration: none;
+}