ci: Support Python 3.13

Minimal/fallback support for `3.13`.

Ideally I'd like to minimise hard dependencies we have on `typing_extensions` before October 2024.
However, this would be the simpler option if it passes CI

Resolves #3587

.github/workflows/build.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
         jsonschema-version: ["3.0", "latest"]
     name: py ${{ matrix.python-version }} js ${{ matrix.jsonschema-version }}
     steps:
@@ -16,6 +16,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
+          allow-prereleases: true
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip

pyproject.toml

@@ -15,7 +15,7 @@ build-backend = "hatchling.build"
 name = "altair"
 authors = [{ name = "Vega-Altair Contributors" }]
 dependencies = [
-    "typing_extensions>=4.10.0; python_version<\"3.13\"",
+    "typing_extensions>=4.10.0; python_version<\"3.14\"",
     "jinja2",
     # If you update the minimum required jsonschema version, also update it in build.yml
     "jsonschema>=3.0",
@@ -46,6 +46,7 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Typing :: Typed",
 ]
 
@@ -145,7 +146,7 @@ features = ["all", "dev", "doc"]
 default-args = ["--numprocesses=logical","--doctest-modules", "tests", "altair"]
 parallel = true
 [[tool.hatch.envs.hatch-test.matrix]]
-python = ["3.8", "3.9", "3.10", "3.11", "3.12"]
+python = ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
 [tool.hatch.envs.hatch-test.scripts]
 run = [
     "ruff check .",