Added language and theme settings.

components/settings/LanguageSetting.js

@@ -0,0 +1,31 @@
+import React from 'react';
+import { FormattedMessage } from 'react-intl';
+import DropDown from 'components/common/DropDown';
+import Button from 'components/common/Button';
+import useLocale from 'hooks/useLocale';
+import { DEFAULT_LOCALE } from 'lib/constants';
+import styles from './TimezoneSetting.module.css';
+import { languages } from '../../lib/lang';
+
+export default function LanguageSetting() {
+  const { locale, saveLocale } = useLocale();
+  const options = Object.keys(languages).map(key => ({ ...languages[key], value: key }));
+
+  function handleReset() {
+    saveLocale(DEFAULT_LOCALE);
+  }
+
+  return (
+    <>
+      <DropDown
+        menuClassName={styles.menu}
+        value={locale}
+        options={options}
+        onChange={saveLocale}
+      />
+      <Button className={styles.button} size="small" onClick={handleReset}>
+        <FormattedMessage id="label.reset" defaultMessage="Reset" />
+      </Button>
+    </>
+  );
+}