Minor style changes for more clarity

I raised this point long time ago and some good changes were done, but I would like to discuss it again to push further some of the changes.

- **Bigger titles** (headers)
- All titles need **better spacing** with subsequent paragraphs. At the moment everything is quite crowded, which makes it more difficult to distinguish sections.
- I would like to have a **more prominent "Notes"**, probably with a surrounded box and maybe an icon too
- Maybe **screenshots need to be bordered** with a thin line

Thanks

Start by reviewing the documentation site's existing styling and the earlier changes referenced in this issue. Compare heading sizes and spacing, Notes presentation, and screenshot borders across the generated pages; done means the agreed visual changes are consistently applied.

Written by the indexing model from the issue text.