[fix] Added keys to mapped lists.

src/Socials.js

@@ -26,8 +26,12 @@ let Socials = () => {
 
   return (
     <div className="socials">
-      {socialItems.map((item) =>
-        <a href={ item.url } className={`socials-i ${ item.icon }`}>{ item.title }</a>
+      {socialItems.map((item, index) =>
+        <a
+          className={`socials-i ${ item.icon }`}
+          key={ index }
+          href={ item.url }
+        >{ item.title }</a>
       )}
     </div>
     );

src/index.js

@@ -45,11 +45,12 @@ const navigationData = [
 const NavigationLinks = () => {
 
   return (
-    navigationData.map((item) =>
+    navigationData.map((item, index) =>
       <NavLink
         activeClassName="active"
         className="link"
         exact
+        key={ index }
         to={item.url}
       >
         <i className={`link-icon ${ item.icon }`} /><span className='link-text'>{item.title}</span>