Mikhail Zolotukhin authored Jan 04, 2022 and Carl Schwan committed Jan 04, 2022

## Summary

This MR splits the docs into three categories according to the proposal in #64. This makes navigating to the tutorials for the different type of developers easier.

The three categories are:
- For the core devs, that build official KDE stuff
- For the extension developers, that make the various extensions: themes, plasmoids, KWin and Plasma scripts etc.
- For the external devs, that use KDE Frameworks and other tech in 3rd party projects, that do not necessary extend or develop the existing KDE tech (i.e. their product is not an extension for KDE project and not the official KDE project).

Each category assumes, that the reader may refer to the upper one, making some kind of matryoshka: the things external dev may know is inside the extension related thing, which is inside the core devs' category.

## Screenshots


![Screen_Shot_2021-11-23_at_19.25.07](/uploads/12452cd5f09452b5eea395e56d83879d/Screen_Shot_2021-11-23_at_19.25.07.png)

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