Added alternative key binding for "Increase Font Size"

This commits adds the "CTRL SHIFT =" as key to increase font size.
The old shortcut "CTRL +" is still active, but it's not always
possible to produce it if the keyboard layout doesn't have the + key
on the base layer.

This add the possibility to compose "CTRL +" when the keyboard has
the "+" available as "SHIFT =", that seems to be very common in
many layouts.

Fix arduino#6806

Author: cmaglie

app/src/processing/app/Editor.java

@@ -1397,12 +1397,15 @@ public void actionPerformed(ActionEvent e) {
     JMenuItem increaseFontSizeItem = newJMenuItem(tr("Increase Font Size"), KeyEvent.VK_PLUS);
     increaseFontSizeItem.addActionListener(event -> base.handleFontSizeChange(1));
     menu.add(increaseFontSizeItem);
-
-    JMenuItem decreaseFontSizeItem = newJMenuItem(tr("Decrease Font Size"), '-');
-    decreaseFontSizeItem.addActionListener(new ActionListener() {
-        public void actionPerformed(ActionEvent e) {
-          base.handleFontSizeChange(-1);
-        }
+    // Add alternative shortcut "CTRL SHIFT =" for keyboards that haven't the "+" key
+    // in the base layer. This workaround covers all the keyboards that have the "+"
+    // key available as "SHIFT =" that seems to be very common.
+    KeyStroke ctrlShiftEq = KeyStroke.getKeyStroke(KeyEvent.VK_EQUALS, SHORTCUT_KEY_MASK | ActionEvent.SHIFT_MASK);
+    menu.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(ctrlShiftEq, "IncreaseFontSize");
+    menu.getActionMap().put("IncreaseFontSize", new AbstractAction() {
+      public void actionPerformed(ActionEvent e) {
+        base.handleFontSizeChange(1);
+      }
     });
     menu.add(decreaseFontSizeItem);