build(pyproject): declare requires-python via PEP 621 [project] metadata

  Add a minimal `[project]` table to `pyproject.toml` and set:

  - `requires-python = ">=3.9"`
  - `name = "folium"`
  - `dynamic = [...]` for fields still sourced from `setup.py`

  Why this is needed:
  `python_requires` in `setup.py` is not enough for tools that read interpreter
  constraints from `pyproject.toml` metadata. Per PEP 621, `requires-python`
  belongs in `[project]`, which allows `uv` to resolve/lock against the correct
  Python range instead of defaulting incorrectly (see
  astral-sh/uv#11424).

Author: Charley-Peng

pyproject.toml

@@ -2,6 +2,21 @@
 requires = ["setuptools>=41.2", "setuptools_scm", "wheel"]
 build-backend = "setuptools.build_meta"
 
+[project]
+name = "folium"
+dynamic = [
+    "version",
+    "description",
+    "readme",
+    "license",
+    "authors",
+    "keywords",
+    "classifiers",
+    "dependencies",
+    "optional-dependencies",
+]
+requires-python = ">=3.9"
+
 [tool.interrogate]
 ignore-init-method = true
 ignore-init-module = false