update CI workflow to use Ubuntu 22.04 and actions/checkout@v4

Author: zebapy

.github/workflows/ci.yml

@@ -17,12 +17,12 @@ jobs:
   # This workflow contains a single job called "build"
   build:
     # The type of runner that the job will run on
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-22.04
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install dependencies
         run: npm install
       - name: Test & check coverage