Update CI to run on dev branch and add Ruby 4.0

Author: cfis

.github/workflows/mri.yml

@@ -2,7 +2,7 @@ name: CI
 
 on:
   push:
-    branches: [ master ]
+    branches: [ master, dev ]
   pull_request:
     branches: [ master ]
 
@@ -21,7 +21,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        ruby: ['3.2', '3.3', '3.4']
+        ruby: ['3.2', '3.3', '3.4', '4.0']
     steps:
       - uses: actions/checkout@v4
       - name: Set up Ruby