Replace <p> by <figure> around images and make tables responsive using table-responsive Bootstrap class

functions.php

/**
* Replace <p> by <figure> around images and make tables responsive using table-responsive Bootstrap class
 */
add_filter( 'the_content', function($content) {
    $content = preg_replace('/<p>\\s*?(<a .*?><img.*?><\\/a>|<img.*?>)?\\s*<\\/p>/s', '<figure class="content-image">$1</figure>', $content);
    
    // Run only if is a singular post page
    if (is_singular()) {
        $content = preg_replace("/(<table(?s).*<\/table>)/i", "<div class='table-responsive'>$1</div>", $content);
    }

    return $content;
}, 30 );