Add workflow for publishing releases

.github/workflows/publish.yml

@@ -0,0 +1,39 @@
+---
+name: Publish to PyPI
+
+"on":
+  push:
+    branches:
+      - 'master'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    environment: release
+    permissions:
+      id-token: write
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: '3.x'
+          cache: 'pip'
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install hatch
+      - name: Build package
+        run: hatch build
+      - name: Test package
+        run: hatch run test
+      - name: Publish package distributions to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        if: github.event_name == 'push' && startsWith(github.ref, 'refs/heads/2')

.gitignore

@@ -24,3 +24,4 @@ ChangeLog
 testtools/_version.py
 man/testtools.1
 man
+.mypy_cache/