Custom CSS property pre-fix breaks in v14

# Bug Report

## Prerequisites

* [ ] Can you reproduce the problem on TYPO3 v11.5 LTS
* [x] Can you reproduce the problem on TYPO3 v12.4 LTS
* [x] Did you [perform a cursory search](https://github.com/issues?q=is%3Aissue+user%3Abenjaminkott+repo%3Abenjaminkott%2Fbootstrap_package)
to see if your bug or enhancement is already reported?

## Description

Version 14 sets a few custom properties using the hardcoded bootstrap prefix `--bs`. In Version 13, this was not the case (or at least not for the components I've been using). So if we override the default bootstrap prefix using this the followin scss configuration, the design will break.

```scss
$prefix: my-root-;
```

The following scss components are using `bs` instead of `#{$prefix}`:

- `_dropdown.scss`
- `_focus-ring.scss`
- `_accordion.scss`
- `_button.scss`
- `_dropdown.scss`
- `_transition.scss`

## Steps to Reproduce

1. Set custom prefix via SASS variable
2. Try overwriting custom properties with the new prefix
3. See style not working

### Expected behavior

All components define and use custom properties relativ to `$prefix`. So styles will be applied.

### Actual behavior

Styles can't be overriden using a custom - custom properties - prefix.

### Screenshots

## Versions

latest