…cal example app for testing (graphql-python#1418)

* Add venv and .venv to gitignore since common venv paths

* Update cookbook-plain app requirements and local-dev notes

This also adds the DEFAULT_AUTO_FIELD to the app's Django settings to
resolve this warning when running `migrate`:

```
ingredients.Category: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
	HINT: Configure the DEFAULT_AUTO_FIELD setting or the IngredientsConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
```

* Fix graphql-python#1417 graphiql explorer styles by including official CSS

Like in the official graphiql-plugin-explorer example here
https://github.com/graphql/graphiql/blob/619864691941c46cc0b0848e8713028e20212c36/packages/graphiql-plugin-explorer/examples/index.html#L26-L29

Resolves graphql-python#1417

* Update GraphiQL version

---------

Co-authored-by: Steven DeMartini <sjdemartini@users.noreply.github.com>
Co-authored-by: Kien Dang <mail@kien.ai>

…sri param to render_graphiql function of the GraphQlView (#1418) (#1460)