Add Navbar component, emotion for css and storybook

front/src/stories/layout/NavItem.stories.tsx

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+import { MemoryRouter } from 'react-router-dom';
+
+import NavItem from '../../layout/NavItem';
+
+export default {
+  title: 'NavItem',
+  component: NavItem,
+};
+
+export const NavItemDefault = () => (
+  <MemoryRouter>
+    <NavItem label="Test" to="/test" />
+  </MemoryRouter>
+);
+
+export const NavItemActive = () => (
+  <MemoryRouter initialEntries={['/test']}>
+    <NavItem label="Test" to="/test" active={true} />
+  </MemoryRouter>
+);

front/src/stories/layout/Navbar.stories.tsx

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+import { MemoryRouter } from 'react-router-dom';
+
+import Navbar from '../../layout/Navbar';
+
+export default {
+  title: 'Navbar',
+  component: Navbar,
+};
+
+export const NavbarOnPerformance = () => (
+  <MemoryRouter initialEntries={['/performances']}>
+    <Navbar />
+  </MemoryRouter>
+);