More verbose and complete docker tutorial (#187)

This partially fixes #183 

* No need to have PHP/composer installed
* More details

README.md

@@ -17,16 +17,40 @@ cd ./my-project
 
 ## Docker
 
-You can also use Docker to setup a new Pimcore Installation:
+You can also use Docker to setup a new Pimcore Installation.
+You don't need to have a PHP environment with composer installed.
+
+### Prerequisits
+
+* Your user must be allowed to run docker commands (directly or via sudo).
+* You must have docker-composed installed.
+* Your user must be allowed to change file permissions (directly or via sudo).
+
+### Follow these steps
+
+1. Initialize the demo project using the `pimcore/pimcore` image
+    ``docker run --rm -v `pwd`:/var/www/html pimcore/pimcore:PHP7.4-apache composer create-project pimcore/demo my-project``
+1. Fix permissions of the created directory (we are already working on a fix to make this redundant)
+    `sudo chown -R 1000 my-project/`
+1. Go to your new project
+    `cd my-project/`
+1. Part of the new project is a docker compose file. Use it to start the needed services
+    `docker-compose up -d`
+1. Install pimcore and initialize the DB
+    `docker-compose exec php vendor/bin/pimcore-install --mysql-host-socket=db`
+    * When asked for admin user and password: Choose freely
+    * When asked for DB credentials, use the following:
+      * MySQL username: pimcore
+      * MySQL password: pimcore
+      * MySQL database: pimcore
+    * This can take a while, up to 20 minutes
+1. Fix permissions again, the installer has created new directories
+    `sudo chown -R 1000 .`
+1. :heavy_check_mark: DONE - You can now visit your pimcore-demo:
+    * The frontend: <http://localhost>
+    * The admin interface, using the credentials you have chosen above:
+      <http://localhost/admin>
 
-```bash
-COMPOSER_MEMORY_LIMIT=-1 composer create-project pimcore/demo my-project
-cd ./my-project
-docker-compose up -d
-docker-compose exec php vendor/bin/pimcore-install --mysql-host-socket=db
-```
-
-The default docker-compose comes with PHP7.4 on debian-buster and mariadb 10.4.
 
 ## Other demo/skeleton packages
 - [Pimcore Skeleton](https://github.com/pimcore/skeleton/)