Support Ruby 3.1 through 3.4

This drops support for Ruby 3.0 which is EOL.

.github/workflows/ruby.yml

@@ -20,7 +20,7 @@ jobs:
 
     strategy:
       matrix:
-        ruby: ["3.0", "3.1", "3.2", "3.3"]
+        ruby: ["3.1", "3.2", "3.3", "3.4"]
 
     steps:
       - uses: actions/checkout@v4

.rubocop.yml

@@ -10,7 +10,7 @@ require:
 
 AllCops:
   NewCops: enable
-  TargetRubyVersion: 3.0
+  TargetRubyVersion: 3.1
 
 # Put development dependencies in the gemspec so rubygems.org knows about them
 Gemspec/DevelopmentDependencies:

gir_ffi-gtk.gemspec

@@ -11,8 +11,9 @@ Gem::Specification.new do |spec|
   spec.summary = "GirFFI-based Ruby bindings for Gtk+ 2 and 3"
   spec.description = "Bindings for Gtk+ 2 and 3, generated by GirFFI, with overrides."
   spec.homepage = "http://www.github.com/mvz/gir_ffi-gtk"
+
   spec.license = "LGPL-2.1+"
-  spec.required_ruby_version = ">= 3.0.0"
+  spec.required_ruby_version = ">= 3.1.0"
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = "https://github.com/mvz/gir_ffi-gtk"