docs: fix development setup instructions in README.md

setup-db.py requires a third argument as it also allows to update a
database so 0 needs to be explicitly given for full initialization.
(TODO: maybe default to 0 if not provided?)

It also requires the database uri in order to properly initalize the
database. The secret key is not necessary for the operation but needed
for the application initalization.

README.md

@@ -5,11 +5,13 @@ Open source form application made with pure HTML/CSS/JS. Needs minimal client-si
 ## Setup
 
 ```sh
+export SQLALCHEMY_DATABASE_URI="sqlite:///test.db"
+export SECRET_KEY="fiesta"
 python3 -m venv venv && source venv/bin/activate
 pip install -r requirements.txt
-python3 setup-db.py
+python3 setup-db.py 0
 
 # Run with:
 source venv/bin/activate
-FLASK_APP=formie FLASK_ENV=development SQLALCHEMY_DATABASE_URI="sqlite:///test.db" SECRET_KEY="fiesta" flask run
+FLASK_APP=formie FLASK_ENV=development flask run
 ```