CI: add Python 3.12 alphas

Closes: #9
Signed-off-by: Sam James <sam@gentoo.org>

Author: thesamesam

.github/workflows/ci.yaml

@@ -4,7 +4,7 @@ jobs:
   build:
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11",
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12-dev",
                          "pypy-3.7", "pypy-3.8", "pypy-3.9"]
       fail-fast: false
     runs-on: ubuntu-latest