Add 4.0 in CI

* Needs a newer rake

Author: eregon

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ ubuntu-latest, windows-latest ]
-        ruby: [ '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', jruby, truffleruby ]
+        ruby: [ '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', '4.0', jruby, truffleruby ]
         exclude:
         - { os: windows-latest, ruby: jruby }
         - { os: windows-latest, ruby: truffleruby }

Gemfile

@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-gem 'rake', '~> 12.3'
+gem 'rake'
 
 group :test do
   gem 'rspec', '~> 3'

Gemfile.lock

@@ -5,7 +5,7 @@ GEM
     docile (1.1.5)
     json (2.3.0)
     json (2.3.0-java)
-    rake (12.3.3)
+    rake (13.3.1)
     rspec (3.12.0)
       rspec-core (~> 3.12.0)
       rspec-expectations (~> 3.12.0)
@@ -31,7 +31,7 @@ PLATFORMS
   x86-mingw32
 
 DEPENDENCIES
-  rake (~> 12.3)
+  rake
   rspec (~> 3)
   simplecov