* extend Y001 to cover `ParamSpec` and `TypeVarTuple` in addition to `TypeVar`
* detect usage of non-integer indices in `sys.version_info` checks
* extend Y010 to check async functions in addition to normal functions
* extend Y010 to cover what was previously included in Y090 (disallow
assignments in `__init__` methods) and Y091 (disallow `raise`
statements). The previous checks were disabled by default.
* introduce Y016 (duplicate union member)
* introduce Y017 (disallows assignments with multiple targets or non-name targets)
* introduce Y018 (detect unused `TypeVar`s)
* introduce Y019 (detect `TypeVar`s that should be `_typeshed.Self`, but aren't)
* introduce Y020 (never use quoted annotations in stubs)
* introduce Y021 (docstrings should not be included in stubs)
* introduce Y022 (prefer stdlib classes over `typing` aliases)
* introduce Y023 (prefer `typing` over `typing_extensions`)
* introduce Y024 (prefer `typing.NamedTuple` to `collections.namedtuple`)
* introduce Y026 (require using `TypeAlias` for type aliases)
* introduce Y025 (always alias `collections.abc.Set`)
* introduce Y027 (Python 2-incompatible extension of Y022)
* introduce Y028 (Use class-based syntax for `NamedTuple`s)
* introduce Y029 (never define `__repr__` or `__str__`)
* introduce Y030 (use `Literal['foo', 'bar']` instead of `Literal['foo'] | Literal['bar']`)
* introduce Y031 (use class-based syntax for `TypedDict`s where possible)
* all errors are now enabled by default
* remove Y092 (top-level attribute must not have a default value)
* `attrs` is no longer a dependency
* `ast_decompiler` has been added as a dependency on Python 3.8 and 3.7
* support Python 3.10
* discontinue support for Python 3.6