Add Python 3.15-dev to test matrix

Author: simonw

.github/workflows/test.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15-dev"]
         numpy: [0, 1]
         os: [ubuntu-latest, macos-latest, windows-latest, macos-14]
     steps: