Improve Smarty 5 documentation

[wisskid]

Smarty 5 documentation still contains references to pages such as https://smarty-php.github.io/smarty/5.x/programmers/api-functions/api-config-load/ and one can find these in the search index too.

• [ ] Search for references to programmers/ in the documentation and rewrite these parts.
• [ ] Then delete the entire programmers/ after checking to see if everything is covered in the other docs