Run ruby/ruby doc generation on CI (#1272)

Author: st0012

.github/workflows/ruby-core.yml

@@ -57,3 +57,16 @@ jobs:
       - name: Test RDoc
         run: make -j2 -s test-all TESTS="rdoc --no-retry"
         working-directory: ruby/ruby
+      - name: Generate Documentation with RDoc
+        run: make html
+        working-directory: ruby/ruby
+      # We need to clear the generated documentation to generate them again
+      # with the Prism parser.
+      - name: Clear Generated Documentation
+        run: rm -r .ext/html
+        working-directory: ruby/ruby
+      - name: Generate Documentation with RDoc (Prism parser)
+        run: make html
+        working-directory: ruby/ruby
+        env:
+          RDOC_USE_PRISM_PARSER: true