Get the superuser information before calling createsuperuser

Description

This MR allow to create a command-line without being interrupted by an interactive shell. This is helpful for automation.

If no argument is given, the interactive shell will still pop to ask for the missing information.

README.md

@@ -3,6 +3,8 @@
 This repo is here to help installing Funkwhale using Docker. It follows the
 [multi-container installation documentation][docs-multi-container].
 
+## Usage
+
 To set up your instance, clone this repo and enter the directory, then run the
 script `./setup.sh`.
 
@@ -13,4 +15,9 @@ pass them to it directly. See the help with this command:
 ./setup --help
 ```
 
+## Developer
+
+Prerequisites:
+* docker-compose
+
 [docs-multi-container]: https://docs.funkwhale.audio/installation/docker.html#docker-multi-container