♻️ refactor(App): use react router

this adds `MainPage`

src/App.test.tsx

@@ -1,62 +0,0 @@
-// Imports
-import { describe, it, expect, afterEach } from 'vitest';
-import { render, screen, cleanup } from '@testing-library/react';
-import userEvent  from '@testing-library/user-event';
-
-// To Test
-import App from './App';
-
-// Tests
-describe('Renders main page correctly', async () => {
-    /**
-     * Resets all renders after each test
-     */
-    afterEach(() => {
-        cleanup();
-    });
-
-    /**
-     * Passes - shows title correctly
-     */
-    it('Should render the page correctly', async () => {
-        // Setup
-        await render(<App />);
-        const h1 = await screen.queryByText('Vite + React');
-
-        // Post Expectations
-        expect(h1).toBeInTheDocument();
-    });
-
-    /**
-     * Passes - shows the button count correctly present
-     */
-    it('Should show the button count set to 0', async () => {
-        // Setup
-        await render(<App />);
-        const button = await screen.queryByText('count is 0');
-
-        // Expectations
-        expect(button).toBeInTheDocument();
-    });
-
-    /**
-     * Passes - clicks the button 3 times and shows the correct count
-     */
-    it('Should show the button count set to 3', async () => {
-        // Setup
-        const user = userEvent.setup();
-        await render(<App />);
-        const button = await screen.queryByText('count is 0');
-
-        // Pre Expectations
-        expect(button).toBeInTheDocument();
-
-        // Actions
-        await user.click(button as HTMLElement);
-        await user.click(button as HTMLElement);
-        await user.click(button as HTMLElement);
-
-        // Post Expectations
-        expect(button?.innerHTML).toBe('count is 3');
-    });
-});