suggestion: dry registrations for us lazy registrars

Thanks for building this.

Would it be easy to allow the `__name__` of the callable being passed in as the default, but allowing a `name` kwarg to overwrite it? I started going down a [decorator rabbit-hole on stack overflow](https://stackoverflow.com/questions/653368/how-to-create-a-python-decorator-that-can-be-used-either-with-or-without-paramet) to try and pitch in a solution, but got lost in decorator hell.

Using ```loaders = catalogue.create("mypackage", "loaders")``` as our shared example, here's what things look like at the moment:
```
#passing the name in explicitly
@loaders.register(name='custom_func')
def custom_func(data):
pass
```
vs.
```
#letting the func name itself
@loaders.register
def custom_func(data):
pass
```
vs.
```
#a cool shorthand version
@loaders
def custom_func(data):
pass
```

This was my attempt, but it doesn't accept passing in the name kwarg.

```
class Registry:
callables = {}

def __call__(self, func, name=None):
if not name: name = func.__name__
self.callables[name] = func

def __contains__(self, func):
return func in self.callables

def __repr__(self):
return f"{self.callables}"

loaders = Registry()

#this works fine
@loaders
def custom_func(data):
pass

#this not so much
@loaders(name='blah')
def custom_func(data):
pass
```

What do you think?