Bump required ruby version to 4.0 (#147)

* Bump required ruby version to 4.0

* Add ruby head

Author: biow0lf

.github/workflows/rspec.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["3.1", "3.2", "3.3", "3.4", "4.0"]
+        ruby: ["4.0", "head"]
 
     steps:
       - name: Harden the runner (Audit all outbound calls)

.rubocop.yml

@@ -7,7 +7,7 @@ plugins:
   - rubocop-rspec
 
 AllCops:
-  TargetRubyVersion: 3.1
+  TargetRubyVersion: 4.0
   NewCops: enable
 
 # We use standard as a linter and formatter instead Rubocop.

.standard.yml

@@ -1 +1 @@
-ruby_version: 3.1
+ruby_version: 4.0

errbit_plugin.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |spec|
   spec.description = "Base to create an errbit plugin"
   spec.homepage = "https://github.com/errbit/errbit_plugin"
   spec.license = "MIT"
-  spec.required_ruby_version = ">= 3.1.0"
+  spec.required_ruby_version = ">= 4.0.0"
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage