Re-add responsive theme.

src/App.style.ts

-import { createMuiTheme } from '@material-ui/core/styles';
+import { createMuiTheme, responsiveFontSizes } from '@material-ui/core/styles';
 
-export const muiTheme = createMuiTheme({
+const muiTheme = createMuiTheme({
   palette: {
     primary: {
       main: '#5e5ce4',
@@ -27,3 +27,5 @@ export const muiTheme = createMuiTheme({
     },
   },
 });
+
+export const appTheme = responsiveFontSizes(muiTheme);

src/App.tsx

@@ -4,7 +4,7 @@ import { BrowserRouter as Router, Switch, Route } from 'react-router-dom';
 import { AuthRoutes, NonAuthRoutes } from 'api/routes';
 import { Roles } from 'api/userRoles';
 import { configDjangoCookieName } from 'api/axios/configDjangoCookieName';
-import { muiTheme } from 'App.style';
+import { appTheme } from 'App.style';
 import { withAuthorization } from 'components/Authorization/Authorization';
 import { AuthUser } from 'components/Auth/Auth';
 import { Dashboard } from 'components/Dashboard/Dashboard';
@@ -29,7 +29,7 @@ export const App: FC = () => {
 
   return (
     <div data-testid="App">
-      <ThemeProvider theme={muiTheme}>
+      <ThemeProvider theme={appTheme}>
         <Router>
           <Switch>
             <Route exact path={NonAuthRoutes.home} component={LandingPage} />