Add Placeholder Text To Comment Form Text Area.php

function wpsites_customize_comment_form_text_area($arg) {
    $arg['comment_field'] = '<p class="comment-form-comment"><label for="comment">' . _x( 'Your Feedback Is Appreciated', 'noun' ) . '</label><textarea id="comment" name="comment" placeholder="Please Use Pastebin or Github Gists If You Want To Leave PHP Code In Your Comment. Thanks!"cols="45" rows="1" aria-required="true"></textarea></p>';
    return $arg;
}

add_filter('comment_form_defaults', 'wpsites_customize_comment_form_text_area');