I want to make a responsive theme with Bootstrap 3. However, I need to automatically add the CSS class .img-responsive to every post image because I need the images to be responsive.
Please suggest me what I need to add in WordPress's functions.php file or any other file that will allow me to add the CSS class automatically.
I have the following code, and as the posts are from previous versions ... They did not work ...
What should I do?
<figure class="image"><img class="lazyload p402_hide" alt=""
width="800" height="400" data-sizes="auto" data-
src="https://br.clubnation.club/wp-content/uploads/2020/01/primeira-
loja-oficial-de-harry-potter-sera-aberta-em-nova-york-2.jpg" data-
srcset="https://br.clubnation.club/wp-
content/uploads/2020/01/primeira-loja-oficial-de-harry-potter-sera-aberta-
em-nova-york-2.jpg 328w, https://br.clubnation.club/wp-
content/uploads/2020/01/primeira-loja-oficial-de-harry-potter-sera-
aberta-em-nova-york-3.jpg 380w, https://br.clubnation.club/wp-
content/uploads/2020/01/primeira-loja-oficial-de-harry-potter-sera-
aberta-em-nova-york-4.jpg 528w, https://br.clubnation.club/wp-
content/uploads/2020/01/primeira-loja-oficial-de-harry-potter-sera-
aberta-em-nova-york-5.jpg 704w" />
<figcaption>A loja será inaugurada no próximo verão.
(Fonte: Warner Bros/Divulgação)</figcaption></figure>