Merge/refactor fluent.syntax.yml and fluent.runtime.yml actions into ci.yml

Author: eemeli

.github/workflows/ci.yml

@@ -20,11 +20,31 @@ jobs:
       - run: python -m mypy fluent.syntax/fluent fluent.runtime/fluent
   test:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.7, 3.8, 3.9, pypy3.9]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.9
+          python-version: ${{ matrix.python-version }}
       - run: python -m pip install ./fluent.syntax ./fluent.runtime
       - run: python -m unittest discover -s fluent.syntax
       - run: python -m unittest discover -s fluent.runtime
+  baseline:
+    runs-on: ubuntu-20.04 # https://github.com/actions/setup-python/issues/544
+    strategy:
+      matrix:
+        fluent-syntax:
+          - ./fluent.syntax
+          - fluent.syntax==0.19.0
+          - fluent.syntax==0.18.1 six
+          - fluent.syntax==0.17.0 six
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: 3.6
+      - run: python -m pip install ${{ matrix.fluent-syntax }}
+      - run: python -m pip install ./fluent.runtime
+      - run: python -m unittest discover -s fluent.runtime