Possibility for multiple target/signature-type pairs?

Hello!

First of all, thanks for a great framework!

I have a question. You can specify the target and the signature type when running the `functions-framework` as such:

```
functions-framework --target=my_endpoint --signature-type=cloud-event
```

Is it possible to specify two different targets, with different signature-types?

Assuming I have the following code:

```python
import functions_framework

@functions_framework.http
def my_http_endpoint(request):
return "Hello world!"

@functions_framework.cloud_event
def my_event_endpoint(cloud_event):
return "Hello world!"
```

For instance by specifying multiple pairs:

```
functions-framework --target=my_event_endpoint --signature-type=cloud-event --target=my_http_endpoint --signature-type=http
```