Add Pharo 13 CI script. Update Pharo 12 CI script.

.github/workflows/Pharo12CI.yml

@@ -9,8 +9,6 @@ on:
       - 'main'
   pull_request:
     types: [assigned, opened, synchronize, reopened]
-  schedule:
-    - cron:  '0 12 * * 0'
 
 jobs:
   build:

.github/workflows/Pharo13CI.yml

@@ -0,0 +1,31 @@
+name: 'Pharo 13 CI'
+
+env: 
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+on:
+  push:
+    branches:
+      - 'main'
+  pull_request:
+    types: [assigned, opened, synchronize, reopened]
+  schedule:
+    - cron:  '0 12 * * 0'
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+        smalltalk: [ Pharo64-13 ]
+    runs-on: ${{ matrix.os }}
+    name: ${{ matrix.smalltalk }} on ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: hpi-swa/setup-smalltalkCI@v1
+        with:
+          smalltalk-image: ${{ matrix.smalltalk }}
+      - name: Load in New Image and Run Tests
+        run: smalltalkci -s ${{ matrix.smalltalk }} ${{ matrix.ston }}
+        shell: bash
+        timeout-minutes: 60