Extends #95Closes#82
Adds parsing of new `type` soft keyword for defining type aliases.
Supports type alias statements as defined in PEP 695 e.g.
```python
# A non-generic type alias
type IntOrStr = int | str
# A generic type alias
type ListOrSet[T] = list[T] | set[T]
# A type alias that includes a forward reference
type AnimalOrVegetable = Animal | "Vegetable"
# A generic self-referential type alias
type RecursiveList[T] = T | list[RecursiveList[T]]
```
All type parameter kinds are supported as in #95.
Builds on soft keyword abstractions introduced in https://github.com/RustPython/RustPython/pull/4519
docs.rs failed to build the documentation of the recently released
rustpython-parser 0.2.0 because the build.rs script couldn't write the
parser.rs file because docs.rs builds the documentation in a sandbox
with a read-only filesystem.
This commit fixes this by writing the parser.rs file to the cargo output
directory instead, as recommended by the docs.rs documentation.[1]
Fixes#4436.
[1]: https://docs.rs/about/builds#read-only-directories
