ci: added more building test environments

.github/workflows/standalone-ci.yml

@@ -2,19 +2,18 @@ name: Cpp
 
 on:
   push:
-    branches: 
-      - main
   pull_request:
     branches: 
       - main
 
 jobs:
   build:
-
-    runs-on: ubuntu-18.04
-
+    strategy:
+      matrix:
+        os: [ ubuntu-22.04, ubuntu-20.04, ubuntu-18.04 ]
+    runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Install dependencies
       run: sudo apt-get install -y build-essential cmake libasio-dev
     - name: Build and pack