Update docs with hint about 2.0 development

Replace the old docs index page with a hint where the (for now) 'real'
docs can be found and that HedgeDoc 2.0 is still in development.

Signed-off-by: David Mehren <git@herrmehren.de>

docs/content/index.md

@@ -1,25 +1,11 @@
-# Welcome to the HedgeDoc Documentation
+# Welcome to the HedgeDoc 2 Documentation
 
 ![HedgeDoc Logo](images/hedgedoc_logo_horizontal.svg)
 
-HedgeDoc lets you create real-time collaborative markdown notes. You can test-drive it by visiting
-our [HedgeDoc demo server][hedgedoc-demo].
+🚧⚠️🚧 **HedgeDoc 2.0 is still in development!**  
+You are probably looking for the 1.x docs.  
+Find them in the `master` branch and on [docs.hedgedoc.org](https://docs.hedgedoc.org).
 
-It is inspired by Hackpad, Etherpad and similar collaborative editors. This project originated with the team
-at [HackMD](https://hackmd.io) and now forked into its own
-organisation. [A longer writeup can be read in the history doc](history.md)
-or [you can have a look at an explanitory graph over at our website][hedgedoc-history].
-
-If you have any questions that aren't answered here, feel free to ask us on [Matrix][matrix.org-url], stop by
-our [community forums][hedgedoc-community] or have a look at our [FAQ][hedgedoc-faq].
-
-
-[hedgedoc-demo]: https://demo.hedgedoc.org
-
-[hedgedoc-history]: https://hedgedoc.org/history
-
-[hedgedoc-faq]: https://hedgedoc.org/faq
+If you want to help us to develop HedgeDoc 2, join us on [Matrix][matrix.org-url]!
 
 [matrix.org-url]: https://chat.hedgedoc.org
-
-[hedgedoc-community]: https://community.hedgedoc.org

docs/mkdocs.yml

@@ -14,6 +14,8 @@ nav:
 markdown_extensions:
   - toc:
       permalink: true
+  - admonition
+  - attr_list
 theme:
   name: 'material'
   language: en