Add parsing of type alias statements i.e. the type keyword (#97)

Extends #95
Closes #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

parser/build.rs

@@ -154,6 +154,7 @@ fn gen_phf(out_dir: &Path) {
         .entry("raise", "Tok::Raise")
         .entry("return", "Tok::Return")
         .entry("try", "Tok::Try")
+        .entry("type", "Tok::Type")
         .entry("while", "Tok::While")
         .entry("with", "Tok::With")
         .entry("yield", "Tok::Yield")