Add copilot-setup-steps workflow and Copilot instructions (#286)

Author: Copilot

.github/copilot-instructions.md

@@ -0,0 +1,8 @@
+# Copilot Instructions
+
+Every PR must have no errors from:
+
+```
+bundle exec rubocop
+bundle exec rspec
+```

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,32 @@
+name: Copilot Setup Steps
+
+# Automatically run the setup steps when they are changed to allow for easy validation, and
+# allow manual testing through the repository's "Actions" tab
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+  pull_request:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+      
+jobs:
+  copilot-setup-steps:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: head
+
+      - name: Use ar_main as the Gemfile
+        run: bundle config --global gemfile gemfiles/ar_main.gemfile
+
+      - name: Install dependencies
+        run: bundle install