Support toml spec 1.0.0 (#245)

iarna/toml is unmaintained.
Replaced by smol-toml which is maintained and has the same api

Fixes: #242

Author: eifinger

__tests__/fixtures/pyproject-toml-project/pyproject.toml

@@ -6,5 +6,14 @@ readme = "README.md"
 requires-python = ">=3.11"
 dependencies = []
 
+[dependency-groups]
+dev = [
+  "reuse==5.0.2",
+  {include-group = "lint"},
+]
+lint = [
+  "flake8==4.0.1",
+]
+
 [tool.uv]
 required-version = "==0.5.14"