feature: add next and previous html buttons

[hamza-m-masood]

Thanks for all your hard work 🙏

It would be really nice to have next and previous HTML elements at the end of the blog article. Something like this:

[hamza-m-masood]

@stelcodes this issue can be closed since your amazing blog series work is merged, right?

[hamza-m-masood]

Actually with the current implementation of the blog series feature, I would really like a previous button as well : )