improvement: all app strings now using i18n

frontend/src/App.js

@@ -1,20 +1,32 @@
-import React from "react";
+import React, { useState, useEffect } from "react";
 import Routes from "./routes";
 import "react-toastify/dist/ReactToastify.css";
 
 import { createMuiTheme, ThemeProvider } from "@material-ui/core/styles";
 import { ptBR } from "@material-ui/core/locale";
 
-const theme = createMuiTheme(
-	{
-		palette: {
-			primary: { main: "#1976d2" },
-		},
-	},
-	ptBR
-);
-
 const App = () => {
+	const [locale, setLocale] = useState();
+
+	const theme = createMuiTheme(
+		{
+			palette: {
+				primary: { main: "#1976d2" },
+			},
+		},
+		locale
+	);
+
+	useEffect(() => {
+		const i18nlocale = localStorage.getItem("i18nextLng");
+		const browserLocale =
+			i18nlocale.substring(0, 2) + i18nlocale.substring(3, 5);
+
+		if (browserLocale === "ptBR") {
+			setLocale(ptBR);
+		}
+	}, []);
+
 	return (
 		<ThemeProvider theme={theme}>
 			<Routes />