Add python 3.15, remove python 3.9 from CI (#76)

Add python 3.15 (and 3.15t) to CI, remove python 3.9 from CI and raise
minimum python version in `pyproject.toml`.

Author: ianthomas23

.github/workflows/main.yml

@@ -26,10 +26,10 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t", "3.15", "3.15t"]
         include:
-          #- os: macos-latest
-          #  python-version: "3.14"
+          - os: macos-latest
+            python-version: "3.14"
           - os: windows-latest
             python-version: "3.14"
 
@@ -45,16 +45,13 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: Install package with test dependencies
-      # matplotlib is not a dependency but tests need it
       run: |
         pip install .[test]
-        pip install matplotlib
 
     - name: Test installation without nbdime
       run: pytest -v
 
     - name: Test Build
-      if: ${{ matrix.python-version == '3.14' }}
       run: |
         pip install build
         python -m build

pyproject.toml

@@ -22,7 +22,7 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
-    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.15",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python",
     "Topic :: Multimedia :: Graphics",
@@ -42,7 +42,7 @@ keywords = [
 license = "BSD-3-Clause"
 license-files = ["LICENSE"]
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 
 [project.entry-points."matplotlib.backend"]
 inline = "matplotlib_inline.backend_inline"