Lack of Style Options for Spaces Between Key and Description in Short Help View

https://github.com/charmbracelet/bubbles/blob/a9344b59531d1b947978485dea07c5597299889a/help/help.go#L132-L134

First, thank you for your work on this package.

In the ShortHelpView function, the space between the key and description does not have dedicated style options. This results in inconsistent styling, especially when a custom background color is applied to the terminal when using the alt window for a full screen TUI. As shown in the attached screenshot, the spaces remain unstyled with no ability to apply custom styles, which leads to visual discrepancies. All other parts of the help component have configurable styles, but these spaces do not, limiting the ability to achieve a consistent look and feel.

Screenshot:

To resolve this issue, I suggest the following approach:

- **Apply Separator Style**: Use the existing SeparatorStyle to style the spaces between the key and description.
Alternatively, you could:
- **Add a Whitespace Style**: Introduce a WhitespaceStyle to style the spaces between the key and description, similar to the JoinHorizontal and JoinVertical methods.

If you settle on an approach, I'm happy to implement it and provide a PR. Thank you for considering this enhancement.