checkbox_options: class-option

[HeikoStudt]

The plugin checkbox_options does prepend a checkbox to the rendered options.

However, I would like to set its CSS classes for styling (basing on Bootstrap 5) e.g. the content into columns. So, it would be nice to have plugin configuration for the checked/unchecked CSS classes.

While at it, I would add an option whether to prepend or append as well.

What do you think?

[HeikoStudt]

I've written code which does add checkedClassName and uncheckedClassName as options, plus append/prepend, and additionally adds a possibility to set the checkbox'es ID so that the custom-render function can create the label for it.

I will be able to provide a PR, if you like.

[HeikoStudt]

I believe, it is not necessary to differ between checked and unchecked class lists. There are no important special bootstrap classes for checked (to automatic style) and any custom styling can use the power of pseudo :checked.
If you accord, I will modify the PR accordingly.