caches conan dependencies in github action

Author: EAlexJ

.github/workflows/ci-compile.yml

@@ -31,6 +31,12 @@ jobs:
 
       - name: Update submodules
         run: git submodule update --init --recursive
+        
+      - name: Cache Conan
+        uses: actions/cache@v4
+        with:
+          path: ~/.conan2
+          key: conan-${{ runner.os }}-unit-cpp${{ matrix.cpp_std }}-${{ hashFiles('conanfile.py') }}
 
       - name: Install dependencies
         run: |