Split out rspec and standardrb GitHub actions

By keeping these separate, we can more easily tell at-a-glance what is causing a GitHub action failure.

This also allows the `spec` and `standard` rake tasks to run in parallel as separate actions. Previously, the combined action simply ran `rake` which would run specs and then only ran standard when specs passed.

.github/workflows/main.yml → .github/workflows/rspec.yml

@@ -1,4 +1,4 @@
-name: Ruby
+name: rspec
 
 on:
   push:
@@ -24,5 +24,5 @@ jobs:
         ruby-version: ${{ matrix.ruby }}
         bundler-cache: true
         cache-version: 1
-    - name: Run the default task
-      run: bundle exec rake
+    - name: Run RSpec
+      run: bundle exec rake spec

.github/workflows/standardrb.yml

@@ -0,0 +1,23 @@
+name: standardrb
+
+on:
+  push:
+    branches:
+      - main
+
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 3.3.1
+          bundler-cache: true
+          cache-version: 1
+      - name: Run Standard Ruby
+        run: bundle exec rake standard