Is your feature request related to a problem? Please describe.

Since version 4.2, Bot API added poll message support, and PTB has also followed up with that in the API. However, as of PTB 12.2.0, ther is no support of poll messages in built in filters like other message types.

Describe the solution you'd like

Add a filter telegram.ext.filters.Filters.poll, namely:

    class _Poll(BaseFilter):
        name = 'Filters.poll'

        def filter(self, message):
            return bool(message.poll)

    poll = _Poll()
    """Messages that contain :class:`telegram.Poll`."""

Describe alternatives you've considered

I’m having this filter in my own code so far.

Additional context

None