feat: create a passage pop up

src/main/java/edu/ntnu/idatt2001/group_30/paths/view/components/pop_up/PassagePopUp.java

+package edu.ntnu.idatt2001.group_30.paths.view.components.pop_up;
+
+import edu.ntnu.idatt2001.group_30.paths.model.Passage;
+import javafx.geometry.Pos;
+import javafx.scene.control.*;
+import javafx.scene.layout.VBox;
+
+public class PassagePopUp {
+
+    private TextField titleField;
+    private TextArea contentArea;
+    private Button saveButton;
+
+    public PassagePopUp() {
+        titleField = new TextField();
+        titleField.setPromptText("Enter the title of the passage");
+
+        contentArea = new TextArea();
+        contentArea.setPromptText("Enter the content of the passage");
+
+        saveButton = new Button("Save");
+
+        VBox content = new VBox(
+                new Label("Passage Title:"),
+                titleField,
+                new Label("Passage Content:"),
+                contentArea,
+                saveButton
+        );
+
+        content.setAlignment(Pos.CENTER);
+        content.setSpacing(20);
+
+        PopUp<VBox, ?> popUp = PopUp
+                .<VBox>create()
+                .withTitle("Create a Passage")
+                .withoutCloseButton()
+                .withContent(content)
+                .withDialogSize(400, 500);
+
+        saveButton.setOnAction(e -> {
+            if (titleField.getText().isBlank() || contentArea.getText().isBlank()) {
+                AlertDialog.showWarning("The title or content cannot be blank.");
+            } else {
+                Passage newPassage = new Passage(titleField.getText(), contentArea.getText());
+
+                //TODO: save the new passage
+                popUp.close();
+            }
+        });
+
+        popUp.showAndWait();
+    }
+}