I have built a website (using GitHub pages) which contains a lot of sub-pages. Almost each one of these pages contains the following same content, e.g. footer part like this:
<footer id="content-info" class="container" role="contentinfo">
...
</footer>
My question is: how to extract this shared same part out to a separate file for reusing? Then I can simply somehow include this file wherever I need to contain the footer part. If this is possible, I can easily edit this part once and all pages that contain it will change automatically.