There is no way how to navigate to HTML Text Editor's toolbar using keyboard.

Users should be allowed to navigate to the toolbar by:
1. CTRL + TAB / CTRL + SHIFT + TAB
    - once focus is in the toolbar, 2D traversal (Up/Down/Right/Left) should be sufficient unless these keystrokes are consumed by other controls
    - note that TAB key is reserved for inserting Tab in Rich Text Editor
2. F10
    - note that this shortcut is used for quick access to Menu bar
    - because HTML Rich Text Editor does not have a Menu bar, we could use this shortcut for focusing the first button in the toolbar
    - if someone use HTML Text Editor control for an app with a Menu bar, pressing F10 should focus the first menu in the Menu bar and not the first button in the toolbar