Configure Github Actions to run tests for multiple OS

Author: ono-max

.github/workflows/protocol.yml

@@ -16,12 +16,13 @@ on:
 jobs:
   test:
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 10
     strategy:
       fail-fast: false
       matrix:
         ruby-version: ['2.6', '2.7', '3.0', '3.1', 'head', 'debug']
+        os: [macos-latest, ubuntu-latest, windows-latest]
 
     steps:
     - uses: actions/checkout@v2

.github/workflows/ruby.yml

@@ -16,12 +16,13 @@ on:
 jobs:
   test:
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 15
     strategy:
       fail-fast: false
       matrix:
         ruby-version: ['2.6', '2.7', '3.0', '3.1', 'head', 'debug']
+        os: [macos-latest, ubuntu-latest, windows-latest]
 
     steps:
     - uses: actions/checkout@v2