Update/enhance documentation

[hansb001]

Based on discussions in Dusseldorf, we must review the existing documentation.

• The structure is not always clear
• hard to find topics
• not always updated to latest versions
• missing parts

[hansb001]

see also: thin-edge/thin-edge.io#1238. Detailed steps to take, will be added in community issues:

[hansb001]

Almost all content is available, but needs to be checked if still current and reorganized in the following way:
also directly in github, people will look first there and they will later click on the link to the documentation.

Requirements/prereq guide

Detailed installation guide

Detailed configuration guide

Detailed developer guide, how to extend.

Contribution guide

Getting started guide, like hello world

How to guides and tutorials need to be combined, no difference

Other points of attention:

Website gif (installation) has to be updated

Less text, more images. Images helped with attractiveness and with searching for specific menu options etc.

[hansb001]

thin-edge/thin-edge.io#1412

[hansb001]

currently working on getting started:https://github.com/thin-edge/thin-edge.io/blob/pr/1512/docs/src/tutorials/getting-started.md

[hansb001]

https://github.com/thin-edge/thin-edge.io/blob/pr/1512/docs/src/tutorials/getting-started.md is now under review. Now working on https://github.com/thin-edge/thin-edge.io/blob/pr/1512/docs/src/tutorials/child-device.md