refactor(docs): index: major restructure & begin of content

- moving badge links to the bottom of file as reference
- write first introducing text
- add chapter captions and todos for them

docs/index.md

-[![latest version](https://img.shields.io/badge/dynamic/json?color=green&label=latest%20release&query=%24%5B0%5D.name&url=https%3A%2F%2Ftransfer.hft-stuttgart.de%2Fgitlab%2Fapi%2Fv4%2Fprojects%2F154%2Frepository%2Ftags%3Fper_page%3D1)](https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/-/packages)
-[![pipeline state](https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/badges/master/pipeline.svg)](https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/pipelines)
-[![latest dev pipeline](https://img.shields.io/badge/dynamic/json?color=lightgrey&label=latest%20dev%20pipeline&query=%24%5B0%5D.status&url=https%3A%2F%2Ftransfer.hft-stuttgart.de%2Fgitlab%2Fapi%2Fv4%2F%2Fprojects%2F154%2Fpipelines%3Fper_page%3D1)](https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/-/packages)
-[![License GPLv3](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
-[![Conventional Commits](https://img.shields.io/badge/Conventional%20Commits-1.0.0-orange.svg)](https://conventionalcommits.org)
+[![latest version][badge-latest-tag]][project-packages]
+[![pipeline state][badge-master-pipe]][project-pipelines]
+[![latest dev pipeline][badge-latest-pipe]][project-pipelines]
+[![License GPLv3][badge-gplv3]](https://www.gnu.org/licenses/gpl-3.0)
+[![Conventional Commits][badge-conventional-commits]](https://conventionalcommits.org)
 
 # Unified Ticketing
 
-!!! Todo
-    - generally what this is about
-    - who's responsible for it
+This is the documentation for a Java-library called `unified-ticketing`.
+This lib provides generic interfaces to interact with tickets
+from different ticket systems out of your Java code.
+
+This library is a maven artifact,
+published under the [GNU GPL-v3][gplv3] license.
+The source code is publicly available from the [transfer portal][transferportal] of the [University of Applied Sciences Stuttgart][hfthome].
+
+## What to find where
+
+!!! todo
+    explain how the documentation is structured
+
+## Maintainer
+
+!!! todo
+    Me/University
+
+[badge-conventional-commits]: https://img.shields.io/badge/Conventional%20Commits-1.0.0-orange.svg
+[badge-gplv3]: https://img.shields.io/badge/License-GPLv3-blue.svg
+[badge-latest-pipe]: https://img.shields.io/badge/dynamic/json?color=lightgrey&label=latest%20dev%20pipeline&query=%24%5B0%5D.status&url=https%3A%2F%2Ftransfer.hft-stuttgart.de%2Fgitlab%2Fapi%2Fv4%2F%2Fprojects%2F154%2Fpipelines%3Fper_page%3D1
+[badge-latest-tag]: https://img.shields.io/badge/dynamic/json?color=green&label=latest%20release&query=%24%5B0%5D.name&url=https%3A%2F%2Ftransfer.hft-stuttgart.de%2Fgitlab%2Fapi%2Fv4%2Fprojects%2F154%2Frepository%2Ftags%3Fper_page%3D1
+[badge-master-pipe]: https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/badges/master/pipeline.svg
+[gplv3]: unified-ticketing/license-softlink.md
+[hfthome]: https://www.hft-stuttgart.de
+[project-packages]: https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/-/packages
+[project-pipelines]: https://transfer.hft-stuttgart.de/gitlab/9Lukas5/unified-ticketing/pipelines
+[transferportal]: https://transfer.hft-stuttgart.de