Test making CI run on ubuntu and windows

.github/workflows/ci.yml

@@ -8,7 +8,15 @@ on:
 
 jobs:
   test:
-    runs-on: macos-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - macos-latest
+          - ubuntu-latest
+          - windows-latest
+
+    runs-on: ${{matrix.os}}
 
     steps:
     - uses: actions/[email protected]
@@ -37,5 +45,6 @@ jobs:
 
     - run: npm install
 
-    - run: opam install . --deps-only
-    - run: eval $(opam env) && opam exec -- dune build
+    - run: opam pin add rescript-editor-support.dev . --no-action
+    - run: opam install . --deps-only --with-doc --with-test
+    - run: opam exec -- dune build