update Ruby to 3.0

Author: Karry

.github/workflows/release.yml

@@ -30,7 +30,7 @@ jobs:
             ${{ runner.os }}-gems
       - uses: actions/setup-ruby@v1
         with:
-          ruby-version: '2.6'
+          ruby-version: '3.0'
       - name: Install jekyll
         run: |
           export GEM_HOME=${PWD}/vendor/bundle