🔧 CD: use PyPA publishing action instead of flit publish

As is explained here:

https://docs.pypi.org/trusted-publishers/using-a-publisher/

The "easy way" to publish with PyPI's "Trusted Publisher" feature is to use PyPA's
github action `pypi-publish`. Here we adapt the CD workflow to do so.

Author: mbercx

.github/workflows/cd.yml

@@ -45,5 +45,8 @@ jobs:
         -   name: Install flit
             run: pip install flit~=3.8
 
-        -   name: Build and publish
-            run: flit publish
+        -   name: Build with flit
+            run: flit build
+
+        -   name: Publish to PyPI using Trusted Publishing
+            uses: pypa/gh-action-pypi-publish@release/v1