UPDATE to ruby 4.0.0 (#258)

See [announcement][1].

[1]: https://www.ruby-lang.org/en/news/2025/12/25/ruby-4-0-0-released/

Author: MaximeD

.github/workflows/ruby-gem.yml

@@ -18,10 +18,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - name: Set up Ruby 3.4
+    - name: Set up Ruby 4.0
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 3.4
+        ruby-version: 4.0
 
     - name: Publish to RubyGems
       run: |

.github/workflows/ruby.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        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 ${{ matrix.ruby }}
@@ -33,10 +33,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - name: Set up Ruby 3.4
+    - name: Set up Ruby 4.0
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 3.4
+        ruby-version: 4.0
         bundler-cache: true # 'bundle install' and cache gems
     - name: Lint
       run: make lint

.ruby-version

@@ -1 +1 @@
-3.4.8
+4.0.0

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 Development tools:
 
-* bump to ruby 3.4.8
+* bump to ruby 4.0.0
 * update gems
 
 # v8.1.0 (December 12. 2025)