Simplify storing strings/bytes in a Storage

[Thomas Güttler]

Docs: ​https://docs.djangoproject.com/en/3.1/topics/files/#storage-objects

path = default_storage.save('path/to/file', ContentFile(b'new content'))

Things would be bit easier, if save() would support strings/bytes directly.

This way a developer needs to type and import less code:

`
path = default_storage.save('path/to/file', b'new content')
`

`
path = default_storage.save('path/to/file', 'new unicode string, encoded automatically with utf-8')
`

Would you accept a patch to Storage.save()?