Create generic end action to more easily create custom actions

[oiseauroch]

Current behavior

Creating a new component with body and then as a closing {{end elem="mycustomelement" }} element require to add code in the core of yeswiki to add **customelement** into end.php` file.

Expected behavior

I would like to be ablo to add a custom element without modifying something that could be removed by update.

Proposal

We could had a default case for end element that look for a end() fonction in the extra YesWiki action like this :

            default:
                echo $this->services->get(Performer::class)->run($elem, 'action', [], true);
                break;

• proposition validated
• implementation tested

[oiseauroch]

a new custom action can now be written as :

<?php

use YesWiki\Core\YesWikiAction;

class ColorAction extends YesWikiAction
{

    public function run()
    {
        $class = $this->arguments['class'] ?? '';
        $color = $this->arguments['color'] ?? (empty($class) ? 'var(--neutral-color)': 'var(--' . $class . ')' );

        if ($this->check_end_elem('color')) {
            return "<span class='color-elem' style='color: $color;'>";
        } else {
            return $this->generate_error_msg('color');
        }

    }

    public function end(): string {
        return '</span>';
    }
}

and use like this :

{{color color="#FFFFFF"}}
my colored text
{{end elem="color"}}