macOS: Option+Up/Down Arrow don't traverse to beginning/end of line in JTextArea

Summary

Add support for handling Option+Up or Option+Down key combination on macOS in JTextArea

Problem

Pressing Option+Up or Option+Down key combination in JTextArea is not handled on macOS

Solution

Added support of Option+Up and Option+Down key action in Swing's Default EditorKit class. This requires defining new action names in the public API of DefaultEditorKit.

Specification

javax.swing.text.DefaultEditorKit

+    /**
+     * Name of the {@code Action} for moving the caret
+     * to the beginning of the current line or up to the
+     * beginning of the previous line if the caret is
+     * already at the beginning of the line.
+     * @see #getActions
+     */
+    public static final String beginLineUpAction = "caret-begin-line-and-up";
+
+    /**
+     * Name of the {@code Action} for moving the caret
+     * to the end of the current line or down to the
+     * end of the next line if the caret is already
+     * at the end of the line.
+     * @see #getActions
+     */
+    public static final String endLineDownAction = "caret-end-line-and-down";
+