Add Option to extend the list of immutable calls

[finswimmer]

This PR adds in option to extend the list of immutable calls. Calls to these method as argument defaults no longer raises a B008 warning.

This is useful when using library like fastapi which comes with their own set of immutable calls.

Closes: #203

[cooperlees]

Nice addition as people are always going to create more immutable calls etc. etc. so like the flexibility here.

[finswimmer]

Cool, thanks 👍 Any plans when a new release will arrive?

[cooperlees]

Released now. Thanks for all your contributions.