Editor Customization

I would like to implement a subset of the Vim keybindings for editing code in System Browsers. Here is what I have tried so far.

Create a subclass of the SmalltalkEditor class called VimEditor.
Add the instance variable mode that will hold the string “normal” or “insert”.
Initialize mode to 'insert' by adding the following instance method:
```
initialize
    mode := 'insert'.
```

Implement the class method initializeShortcuts as follows:

initializeShortcuts
    super initializeShortcuts.
    shortcuts
        at: 27 + 1
        put: #switchToCommandMode:.
    "escape key - when in insert mode, switch to command mode"
    shortcuts
        at: 105 + 1
        put: #xKey:.
    "i key - when in command mode, switch to insert mode"
    shortcuts
        at: 120 + 1
        put: #xKey:.
    "x key - when in command mode, delete character under cursor"

Implement the following instance methods:

escapeKey: aKeyboardEvent
    | inCommandMode |
    inCommandMode := mode = 'command'.
    inCommandMode ifFalse: [mode := 'command'].
    "Hopefully returning false means that a superclass can process the event."
    ^ inCommandMode not.

iKey: aKeyboardEvent
    | inCommandMode |
    inCommandMode := mode = 'command'.
    inCommandMode ifTrue: [mode := 'insert'].
    "Hopefully returning false means that a superclass can process the event."
    ^ inCommandMode.

xKey: aKeyboardEvent
    | inCommandMode |
    inCommandMode := mode = 'command'.
    inCommandMode ifTrue: ['delete character under cursor' print].
    "Hopefully returning false means that a superclass can process the event."
    ^ inCommandMode.

TODO: Determine how to modify the System Browser to use VimEditor instead of SmalltalkEditor in its bottom pane.
TODO: Determine how to modify the xKey: method to really delete a character.

Changes will likely have no effect until the image is saved and restarted.