feat(documentation): reogarnized and added doc about notifictions in the frontend.

* Reorganized documentation folder
* Rorganized documentation sidebar in browser
* Added documentation about notifications in the frontend #74
* Tweaks

Bonus: more readable docker-compose
9 jobs for master in 5 minutes and 6 seconds (queued for 16 seconds)
Status Job ID Name Coverage
  Check
passed #472733
docker
check_back

00:00:38

passed #472734
docker
check_front

00:01:09

 
  Test
passed #472735
docker
test_back

00:00:46

89.0%
passed #472736
docker
test_frontend

00:00:56

 
  Lint
passed #472738
docker
eslint

00:00:58

passed #472737
docker
flake8

00:00:11

 
  Svg Gen Docu
passed #472739
docker
generate_UML_svg

00:00:11

 
  Documentation
passed #472740
docker
pages

00:00:13

 
  Deploy
passed pages:deploy

00:00:00