Add downstream tests

.github/workflows/Downstream.yml

@@ -0,0 +1,42 @@
+name: Downstream
+on:
+  push:
+    branches:
+      - main
+    tags: '*'
+  pull_request:
+
+# Needed to allow julia-actions/cache to delete old caches that it has created
+permissions:
+  actions: write
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: downstream ${{ matrix.package }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        package:
+          - 'ClimaAtmos.jl'
+          - 'ClimaCoupler.jl'
+          - 'ClimaDiagnostics.jl'
+          - 'ClimaLand.jl'
+          - 'KinematicDriver.jl'
+          - 'ClimaDiagnostics.jl'
+    steps:
+      - uses: actions/checkout@v4
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: '1.10'
+      - uses: julia-actions/cache@v2
+      - uses: julia-actions/julia-buildpkg@v1
+      - uses: actions/checkout@v4
+        with:
+          repository: 'CliMA/${{ matrix.package }}'
+          path: ${{ matrix.package }}