Add alternative publish workflow

.github/workflows/publish_test.yaml

@@ -0,0 +1,30 @@
+# copied from https://github.com/marketplace/actions/install-poetry-action
+name: mypy
+
+on: pull_request
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+    steps:
+      #----------------------------------------------
+      #       check-out repo and set-up python
+      #----------------------------------------------
+      - name: Check out repository
+        uses: actions/checkout@v3
+      - name: Set up python
+        id: setup-python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.10"
+      #----------------------------------------------
+      #  -----  install & configure poetry  -----
+      #----------------------------------------------
+      - name: Install Poetry
+        uses: snok/install-poetry@v1
+        with:
+          virtualenvs-create: true
+          virtualenvs-in-project: true
+          installer-parallel: true
+      - name: Build ixmp4
+        run: poetry build