* Added full support for the Bot API 9.6
* Add support for `managed_bot` updates
* Set `description_parse_mode` default to `"parse_mode"` and use `DateTime` for `addition_date` in `PollOption`
* Update changelog with features and changes from Bot API 9.6
* Add changelog fragment generator and update poll parameter descriptions
* #1277 Replace datetime.datetime with DateTime across codebase
Replaced all instances of standard library 'datetime.datetime' with a new 'DateTime' type from `.custom` module. This change is necessary to make all date-time values compatible with the Telegram Bot API (it uses Unix time). This will simplify the conversion process and eliminate potential errors related to date-time format mismatches. Changed codebase, butcher files, and modified 'pyproject.toml' to shift the typing-extensions dependency. The 'aiogram/custom_types.py' file was renamed to 'aiogram/types/custom.py' to better reflect its nature as a location for custom types used in the aiogram library.
