pyproject.toml: Allow maturin >= 1.8.0 to fill the version

maturin >= 1.8.0 stopped filling the version from Cargo.toml, because
the spec only allows this, when the metadata key is listed in
`dynamic` [1][2].

Fixes jamesturk#224.

[1] https://packaging.python.org/en/latest/specifications/pyproject-toml/#dynamic
[2] PyO3/maturin#2390

pyproject.toml

@@ -4,6 +4,7 @@ build-backend = "maturin"
 
 [project]
 name = "jellyfish"
+dynamic = ["version"]
 requires-python = ">=3.8"
 classifiers = [
   "Programming Language :: Rust",