Support CTRL + DELETE and CTRL + BACKSPACE to delete word

[Jacalz]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

We should support the common feature of pressing CTRL + BACKSPACE to remove a word to the left and CTRL + DELETE (Option (alt) + backspace on macOS) to delete a word to the right in the Entry widget.

Is it possible to construct a solution with the existing API?

Yes. See #4084 that I dropped due to some bugs I didn't have time to figure out.

Describe the solution you'd like to see.

Implement support for deleting whole words to the right and left with simple keyboard shortcuts.

[sdassow]

Totally in in favor of this idea. What is common though? For a more complete list of different shortcuts: https://en.wikipedia.org/wiki/Table_of_keyboard_shortcuts#Text_editing
In my projects I've been adding CTRL-A/CTRL-E for beginning/end of line jumping for example, so a bit similar to what readline supports.

[Jacalz]

It seems to me like CTRL + Del and CTRL + Backspace seem to be the most common. We just need to make sure that macOS uses the option key instead.

[dweymouth]

On develop for release in 2.5.0