ci: add YAML linting to GitHub Actions workflow

- Install yamllint in the lint job
- Add yaml linting step using .yamllint-ci.yml configuration
- Ensure YAML files follow consistent formatting standards
- Fix PATH issues in Perl dependency installation
- Add yamllint configuration file for CI

Author: josecelano

.github/copilot-instructions.md

@@ -91,4 +91,5 @@ ALWAYS run the linting suite before committing any changes:
 
 ```bash
 markdownlint "**/*.md"
+yamllint -c .yamllint-ci.yml .
 ```

.github/workflows/testing.yml

@@ -18,11 +18,14 @@ jobs:
       - name: Install dependencies
         run: |
           sudo apt-get update
+          sudo apt-get install -y yamllint
           sudo npm install -g markdownlint-cli
 
-      - name: Run linting
+      - name: Run markdown linting
         run: markdownlint "**/*.md"
 
+      - name: Run yaml linting
+        run: yamllint -c .yamllint-ci.yml .
   test:
     runs-on: ubuntu-latest
     name: Test

.yamllint-ci.yml

@@ -0,0 +1,10 @@
+extends: default
+
+rules:
+  line-length:
+    max: 120 # More reasonable for infrastructure code
+  comments:
+    min-spaces-from-content: 1 # Allow single space before comments
+  document-start: disable # Cloud-init files don't need --- start
+  truthy:
+    allowed-values: ["true", "false", "yes", "no", "on", "off"] # Allow cloud-init and GitHub Actions common values