### What does this merge request add?

* Fixes a few links
* Mentions Splash Screen
* Changes from lists to headings + descriptions + lists
* Puts global theme at the top and links to its components

### Screenshot of the result (optional)

(If this merge request introduces a visual change or a new website feature, please **add a screenshot** by using the clip button in the upper right of this editor, otherwise leave this section blank)

### How to test this MR

```bash
git clone https://invent.kde.org/documentation/develop-kde-org.git
cd develop-kde-org
git mr 285
hugo server
```