Drop Ruby 2.6 support

Necessary in order to update to latest indieweb-endpoints gem.

Author: jgarber623

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.6", "2.7", "3.0", "3.1", "3.2", "3.3"]
+        ruby: ["2.7", "3.0", "3.1", "3.2", "3.3"]
     steps:
       - uses: actions/checkout@v5
       - uses: ruby/setup-ruby@v1

.rubocop.yml

@@ -3,3 +3,6 @@ inherit_from:
   - https://rubocop.jgarber.cc/rubocop-rspec.yml
 
 plugins: rubocop-packaging
+
+AllCops:
+  TargetRubyVersion: "2.7"

README.md

@@ -12,11 +12,11 @@
 - Perform [endpoint discovery](https://www.w3.org/TR/webmention/#sender-discovers-receiver-webmention-endpoint) on mentioned URLs.
 - Send webmentions to one or more mentioned URLs (and optionally include a [vouch](https://indieweb.org/Vouch) URL).
 - Verify that a received webmention's source URL links to a target URL (and optionally verify that a vouch URL mentions the source URL's domain).
-- Supports Ruby 2.6 and newer.
+- Supports Ruby 2.7 and newer.
 
 ## Getting Started
 
-Before installing and using webmention-client-ruby, you'll want to have [Ruby](https://www.ruby-lang.org) 2.6 (or newer) installed. Using a Ruby version managment tool like [rbenv](https://github.com/rbenv/rbenv), [chruby](https://github.com/postmodern/chruby), or [rvm](https://github.com/rvm/rvm) is recommended.
+Before installing and using webmention-client-ruby, you'll want to have [Ruby](https://www.ruby-lang.org) 2.7 (or newer) installed. Using a Ruby version managment tool like [rbenv](https://github.com/rbenv/rbenv), [chruby](https://github.com/postmodern/chruby), or [rvm](https://github.com/rvm/rvm) is recommended.
 
 webmention-client-ruby is developed using Ruby 3.4 and is tested against additional Ruby versions using [GitHub Actions](https://github.com/indieweb/webmention-client-ruby/actions).
 

webmention.gemspec

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 Gem::Specification.new do |spec|
-  spec.required_ruby_version = ">= 2.6"
+  spec.required_ruby_version = ">= 2.7"
 
   spec.name = "webmention"
   spec.version = "8.0.0"