chore: add support for ruby 2.6

Author: rieg-ec

.github/workflows/main.yml

@@ -7,7 +7,7 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
-        ruby: ['2.7', '3.0', '3.1', head, jruby, jruby-head, truffleruby, truffleruby-head]
+        ruby: ['2.6', '2.7', '3.0', '3.1', head, jruby, jruby-head, truffleruby, truffleruby-head]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3

md_to_notion.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |spec|
   spec.description = "Convert Markdown and GitHub Flavoured Markdown to Notion API Blocks and RichText."
   spec.homepage = "https://github.com/rieg-ec/md-to-notion"
   spec.license = "MIT"
-  spec.required_ruby_version = ">= 2.7.0"
+  spec.required_ruby_version = ">= 2.6.0"
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = "https://github.com/rieg-ec/md-to-notion"