Fix(Core): add missing check_prerequisites()

[stonebuzz]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

Add missing check_prerequisites()

function plugin_escalade_check_prerequisites()
{
    if (!is_readable(__DIR__ . '/vendor/autoload.php') || !is_file(__DIR__ . '/vendor/autoload.php')) {
        echo "Run composer install --no-dev in the plugin directory<br>";
        return false;
    }

    return true;
}

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