Ship the Python README as the PyPI description

The `vtracer` package never declared a `readme`, so its PyPI page rendered
an empty description. Point `[project].readme` at the crate's README, and
mirror it in Cargo.toml alongside the core crate's convention.

Pin the documented install to 1.0.0a2 while the 1.0 line is pre-release:
`--pre` would resolve it, but a bare `pip install vtracer` still lands on
0.6.15, whose cp314 wheels segfault on any keyword argument (pyo3 0.19
predates CPython 3.14 moving `PyTupleObject::ob_item`, #124).

crates/vtracer-py/pyproject.toml

@@ -5,6 +5,7 @@ build-backend = "maturin"
 [project]
 name = "vtracer"
 description = "Raster to vector graphics converter — Python bindings for the vtracer framework."
+readme = "README.md"
 requires-python = ">=3.8"
 license = { text = "MIT OR Apache-2.0" }
 authors = [{ name = "Chris Tsang", email = "tyt2y7@gmail.com" }]