Add Ruby 4 to test matrix (#707)

* Add Ruby 4 to test matrix

* Changelog entry

* Scheduled runs

* Setup dependabot for updating github actions

Author: anakinj

.github/dependabot.yml

@@ -0,0 +1,7 @@
+---
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/test.yml

@@ -8,6 +8,8 @@ on:
   pull_request:
     branches:
       - "*"
+  schedule:
+    - cron: "0 0 * * 5"
 jobs:
   rubocop:
     name: RuboCop
@@ -39,6 +41,7 @@ jobs:
           - "3.2"
           - "3.3"
           - "3.4"
+          - "4.0"
         gemfile:
           - gemfiles/standalone.gemfile
         experimental: [false]

CHANGELOG.md

@@ -11,6 +11,7 @@
 **Fixes and enhancements:**
 
 - Fix compatibility with the openssl 4.0 gem [#706](https://github.com/jwt/ruby-jwt/pull/706)
+- Test against Ruby 4.0 on CI [#707](https://github.com/jwt/ruby-jwt/pull/707)
 - Your contribution here
 
 ## [v3.1.2](https://github.com/jwt/ruby-jwt/tree/v3.1.2) (2025-06-28)