Allow pinning certain sections in documentation

# Feature request

## Summary

In documentations a lot of times there are sections that consistently exist across most pages of the docs, for instance in the C++ documentation a lot of times you find that there is an Examples section that shows how to use the function being documented. I would really like to have the example section appear on the top of the page because a lot of times it does a much better job at explaining what the function does and how to use it than the cppreference cryptic definitions.

## Examples

I don't have a screenshot of this feature from another source. I think having a pin button next to the sections is a good starting point. When that button is clicked, the section should be added to a list of pinned sections, and whenever the visited page contains that section, it should be displayed at the top of the page. Of course, the pinned sections will be local to each set of docs, so if you pin the Examples section in the C++ docs, it won't be pinned in the CSS docs. This is both simpler to implement and makes sense, since each documentation set has its own structure.

I think this is a solid foundation to build on. From there, you could refine it further, perhaps by adding a settings section in each set of docs where you can view all available sections in those docs and allow the user to drag and drop them into a list to define their preferred order. However, this would 1) be quite challenging to implement and 2) may not be practical in reality.