Correctly override bundle-configuration

[zoglo]

Description

• This PR fixes an issue where trying to override the bundle-configuration via style-manager archives would result in only replacing the first value.

• Also fixes #99

Explanation of the bug

// Overwrite existing value
if (!$key = array_search($field, array_column($arrClasses, 'key')))
{
    $arrClasses[ $key ] = [
        'key' => $cssClass['key'],
        'value' => $cssClass['value']
    ];
}

• $field has always been $field = 'cssClasses' and not the class key
• The return value of array_search has always been false since cssClasses was never within the classlist, thus returning false
• Checking for !false would return true which would trigger the condition
• The $key would be false, $arrClasses[false] is the same as $arrClasses[0] and would replace the index with number 0

The fix

This is fixed with the following code since it'll actually get they $key based on the $cssClass['key'] now. I also changed it to check for false !== $key rather than !$key for type safety

// Overwrite existing value
if (false !== ($key = array_search($cssClass['key'], array_column($arrClasses, 'key'))))
{
    ...

[doishub]

Great, thank you @zoglo!