.github/workflows/ruby.yml in chars-0.3.0 vs .github/workflows/ruby.yml in chars-0.3.1

@@ -7,15 +7,15 @@
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         ruby:
-          - 2.4
-          - 2.5
-          - 2.6
-          - 2.7
-          - 3.0
+          - '2.6'
+          - '2.7'
+          - '3.0'
+          - '3.1'
           - jruby
+          - truffleruby
     name: Ruby ${{ matrix.ruby }}
     steps:
       - uses: actions/checkout@v2
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1