Added functionality

src/main/java/az/araezarzosa/spotifyoverlay/spotify_in_game_overlay/ErrorDialog.java

@@ -0,0 +1,57 @@
+package az.araezarzosa.spotifyoverlay.spotify_in_game_overlay;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.*;
+import java.net.URL;
+
+public class ErrorDialog {
+    public static void showErrorMessage() {
+    	JFrame frame = new JFrame("Error");
+        URL iconURL = App.class.getResource("icon.png");
+		ImageIcon icon = new ImageIcon(iconURL);
+		Image iconImage = icon.getImage();
+		Image resizedImage = iconImage.getScaledInstance(32, 32, Image.SCALE_SMOOTH);
+		frame.setIconImage(resizedImage);
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        frame.setSize(300, 100);
+        frame.setResizable(false);
+        frame.setLayout(new FlowLayout());
+        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
+
+	    JPanel panel = new JPanel();
+	    panel.setLayout(new GridBagLayout());
+	    panel.setBackground(new Color(25, 20, 20));
+
+	    JLabel label = new JLabel("Error: Invalid Input");
+	    label.setFont(new Font("Circular", Font.BOLD, 12));
+	    label.setForeground(new Color(30, 215, 96));
+	    GridBagConstraints labelConstraints = new GridBagConstraints();
+	    labelConstraints.gridx = 0;
+	    labelConstraints.gridy = 0;
+	    labelConstraints.insets = new Insets(0, 0, 10, 0);
+	    panel.add(label, labelConstraints);
+
+        JButton errorButton = new JButton("Ok");
+        errorButton.setFont(new Font("Circular", Font.BOLD, 12));
+        errorButton.setBackground(new Color(30, 215, 96));
+        errorButton.setForeground(Color.BLACK);
+        errorButton.setBorder(BorderFactory.createEmptyBorder());
+        errorButton.setBorderPainted(false);
+        errorButton.setPreferredSize(new Dimension(125, 35)); 
+        GridBagConstraints buttonConstraints = new GridBagConstraints();
+        buttonConstraints.gridx = 0;
+        buttonConstraints.gridy = 1;
+        buttonConstraints.insets = new Insets(0, 0, 10, 0);
+	    panel.add(errorButton, buttonConstraints);
+        errorButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+            	frame.dispose();
+            }
+        });
+        frame.add(errorButton);
+
+        frame.setVisible(true);
+    }
+}