Allow resizing of application window

The layout of the program window is messed up when user attempts to
resize the window.

Changes are made by SceneBuilder configurations to ensure that the
window and the UI elements are anchored properly at the expected
position when user resize the window, so as to enhance user experience

src/main/resources/view/MainWindow.fxml

@@ -8,9 +8,9 @@
 
 <AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="400.0" stylesheets="@../css/main.css" xmlns="http://javafx.com/javafx/22" xmlns:fx="http://javafx.com/fxml/1" fx:controller="gopher.gui.MainWindow">
     <children>
-        <TextField fx:id="userInput" layoutY="558.0" onAction="#handleUserInput" prefHeight="41.0" prefWidth="324.0" AnchorPane.bottomAnchor="1.0" />
-        <Button fx:id="sendButton" layoutX="324.0" layoutY="557.0" mnemonicParsing="false" onAction="#handleUserInput" prefHeight="41.0" prefWidth="76.0" text="Send" textFill="WHITE" />
-        <ScrollPane fx:id="scrollPane" hbarPolicy="NEVER" hvalue="1.0" prefHeight="557.0" prefWidth="400.0" vvalue="1.0">
+        <TextField fx:id="userInput" layoutY="558.0" onAction="#handleUserInput" prefHeight="41.0" prefWidth="324.0" AnchorPane.bottomAnchor="1.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="76.0" />
+        <Button fx:id="sendButton" layoutX="324.0" layoutY="557.0" mnemonicParsing="false" onAction="#handleUserInput" prefHeight="41.0" prefWidth="76.0" text="Send" textFill="WHITE" AnchorPane.bottomAnchor="1.6666666666666643" AnchorPane.rightAnchor="0.0" />
+        <ScrollPane fx:id="scrollPane" fitToWidth="true" hbarPolicy="NEVER" hvalue="1.0" prefHeight="557.0" prefWidth="400.0" vvalue="1.0" AnchorPane.bottomAnchor="42.66666666666663" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
             <content>
                 <VBox fx:id="dialogContainer" prefHeight="552.0" prefWidth="388.0" />
             </content>