feat: build ITree in CI (#47)

Thus ensuring we don't break ITree when making changes to the framework.

In the process, we've cleaned up the CI workflows, by running lake exe cache get only once, in its own step.

.github/workflows/ci.yml

@@ -22,12 +22,14 @@ jobs:
           ~/.elan/bin/lean --version
           echo "$HOME/.elan/bin" >> $GITHUB_PATH
 
-      - name: Compile Library 🧐
-        run: |
-          lake -R exe cache get
-          lake -R build
+      - name: Fetch cached dependencies 🕑
+        run : lake -R exe cache get
 
-      - name: Compile Tests
-        run: |
-          lake -R exe cache get
-          lake -R build +Test
+      - name: Compile QpfTypes library 🧐
+        run: lake -R build
+
+      - name: Compile tests 🧐
+        run: lake -R build +Test
+
+      - name: Compile ITree library 🧐
+        run: lake -R build +ITree

ITree.lean

@@ -0,0 +1 @@
+import ITree.Basic