Add basic theming support.

• Add global styling. Remove the old css file.
• Start on the themes

Issue: GREG-40

frontend/src/App.tsx

-import React, { useState, Suspense } from 'react'
+import React, { useState } from 'react'
 import { useTranslation } from 'react-i18next'
 
 import './App.css'
 
-import './i18n'
 import { Button } from './components/button'
 
 import { appTimezone, appVersion, appTheme } from './appConfig'
@@ -31,48 +30,41 @@ const App = () => {
   }
 
   return (
-    <Suspense fallback="loading">
-      <div className="App">
-        <header className="App-header">
-          <Button href="https://example.com" target="_blank" rel="noopener">
-            Knapp
-          </Button>
-          <Button
-            href="https://example.com"
-            target="_blank"
-            rel="noopener"
-            pink
-          >
-            Rosa knapp
-          </Button>
+    <div className="App">
+      <header className="App-header">
+        <Button href="https://example.com" target="_blank" rel="noopener">
+          Knapp
+        </Button>
+        <Button href="https://example.com" target="_blank" rel="noopener">
+          Rosa knapp
+        </Button>
 
-          <p>{t('common:test')}</p>
-          <p>{t('common:nested.test')}</p>
-          <p>{t('footer:footerInfo')}</p>
+        <p>{t('common:test')}</p>
+        <p>{t('common:nested.test')}</p>
+        <p>{t('footer:footerInfo')}</p>
 
-          <Button
-            onClick={() =>
-              i18n.language === 'en'
-                ? i18n.changeLanguage('nb')
-                : i18n.changeLanguage('en')
-            }
-          >
-            {t('common:language.change', {
-              lang: i18n.language === 'en' ? 'Norsk' : 'Engelsk',
-            })}
-          </Button>
-          <p>
-            Version {appVersion}
-            <br />
-            Timezone {appTimezone}
-            <br />
-            Theme {appTheme}
-            <br />
-            API reachable? {apiHealth}
-          </p>
-        </header>
-      </div>
-    </Suspense>
+        <Button
+          onClick={() =>
+            i18n.language === 'en'
+              ? i18n.changeLanguage('nb')
+              : i18n.changeLanguage('en')
+          }
+        >
+          {t('common:language.change', {
+            lang: i18n.language === 'en' ? 'Norsk' : 'Engelsk',
+          })}
+        </Button>
+        <p>
+          Version {appVersion}
+          <br />
+          Timezone {appTimezone}
+          <br />
+          Theme {appTheme}
+          <br />
+          API reachable? {apiHealth}
+        </p>
+      </header>
+    </div>
   )
 }