CI: test experimental features

Author: dnicolodi

.github/workflows/tests.yml

@@ -99,6 +99,11 @@ jobs:
           - os: ubuntu-latest
             python: '3.12'
             pyproject_metadata: '==0.7.1'
+          # Tets experimental features.
+          - os: ubuntu-latest
+            python: '3.12'
+            pyproject_metadata: '==0.9.0b7'
+            meson: '@git+https://github.com/mesonbuild/meson.git@refs/pull/13783/head'
 
     steps:
       - name: Checkout