What kind of feature are you missing? Where do you notice a shortcoming of PTB?

Calling add_handler multiple times maybe become tedious, so this proposes a new method to add multiple handlers at once.

Describe the solution you'd like

A new method Dispatcher.add_handlers (trailing s!) with the following syntax:

dispatcher.add_handlers(list/sequence_of_handlers, group)

should be a substitute for

for handler in list_of_handlers:
    dispatcher.add_handler(handler, group=group)

and

dispatcher.add_handler({1: [list_1], 2: [list_2]})

should be a shortcut for

for group, handlers in my_dict.items():
    for handler in handlers:
        dispatcher.add_handler(handler, group=group)

Passing the group argument in this case should throw a ValueError

Describe alternatives you've considered

Additional context

Proposed in #2813

If you are interested in PRing for this, please leave a comment here.
For the tests to add, you can get inspiration e.g. here.