chore: update CI matrix

Author: Envek

.github/workflows/test.yml

@@ -14,6 +14,7 @@ jobs:
     if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.owner.login != github.event.pull_request.base.repo.owner.login
     name: 'Ruby ${{ matrix.ruby }}'
     runs-on: ubuntu-latest
+    continue-on-error: ${{ matrix.optional || false }}
     strategy:
       fail-fast: false
       matrix:
@@ -22,8 +23,13 @@ jobs:
           - '3.0'
           - '3.1'
           - '3.2'
+          - '3.3'
+          - '3.4'
+        include:
+          - ruby: head
+          - optional: true
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}