Run RSpec tests in CI. (#2262)

I'm not sure why, but these tests were not being run as part of
our CI build. I think it's good to have some sort of compatibility
tests with RSpec so I opted to keep them vs. removing them.

Author: joelhawksley

Rakefile

@@ -134,4 +134,4 @@ namespace :docs do
   end
 end
 
-task default: [:test, :engine_test]
+task default: [:test, :engine_test, :spec]

docs/CHANGELOG.md

@@ -18,6 +18,10 @@ nav_order: 6
 
     *Joel Hawksley*
 
+* Run RSpec tests in CI.
+
+    *Joel Hawksley*
+
 ## 3.22.0
 
 * Rewrite `ViewComponents at GitHub` documentation as more general `Best practices`.