Add Agentic Workflows as a new resource type

Add support for contributing Agentic Workflows — AI-powered repository
automations that run coding agents in GitHub Actions, defined in markdown
with natural language instructions (https://github.github.com/gh-aw).

Changes:
- Create workflows/ directory for community-contributed workflows
- Add workflow metadata parsing (yaml-parser.mjs)
- Add workflow README generation (update-readme.mjs, constants.mjs)
- Add workflow data to website generation (generate-website-data.mjs)
- Update README.md, CONTRIBUTING.md, and AGENTS.md with workflow docs,
  contributing guidelines, and code review checklists

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

eng/yaml-parser.mjs

@@ -253,6 +253,67 @@ function parseHookMetadata(hookPath) {
   );
 }
 
+/**
+ * Parse workflow metadata from a workflow folder
+ * @param {string} workflowPath - Path to the workflow folder
+ * @returns {object|null} Workflow metadata or null on error
+ */
+function parseWorkflowMetadata(workflowPath) {
+  return safeFileOperation(
+    () => {
+      const readmeFile = path.join(workflowPath, "README.md");
+      if (!fs.existsSync(readmeFile)) {
+        return null;
+      }
+
+      const frontmatter = parseFrontmatter(readmeFile);
+
+      // Validate required fields
+      if (!frontmatter?.name || !frontmatter?.description) {
+        console.warn(
+          `Invalid workflow at ${workflowPath}: missing name or description in frontmatter`
+        );
+        return null;
+      }
+
+      // Extract triggers from frontmatter if present
+      const triggers = frontmatter.triggers || [];
+
+      // List bundled assets (all files except README.md), recursing through subdirectories
+      const getAllFiles = (dirPath, arrayOfFiles = []) => {
+        const files = fs.readdirSync(dirPath);
+
+        files.forEach((file) => {
+          const filePath = path.join(dirPath, file);
+          if (fs.statSync(filePath).isDirectory()) {
+            arrayOfFiles = getAllFiles(filePath, arrayOfFiles);
+          } else {
+            const relativePath = path.relative(workflowPath, filePath);
+            if (relativePath !== "README.md") {
+              arrayOfFiles.push(relativePath.replace(/\\/g, "/"));
+            }
+          }
+        });
+
+        return arrayOfFiles;
+      };
+
+      const assets = getAllFiles(workflowPath).sort();
+
+      return {
+        name: frontmatter.name,
+        description: frontmatter.description,
+        triggers,
+        tags: frontmatter.tags || [],
+        assets,
+        path: workflowPath,
+      };
+    },
+    workflowPath,
+    null
+  );
+}
+
 /**
  * Parse a generic YAML file (used for tools.yml and other config files)
  * @param {string} filePath - Path to the YAML file
@@ -276,6 +337,7 @@ export {
   parseFrontmatter,
   parseSkillMetadata,
   parseHookMetadata,
+  parseWorkflowMetadata,
   parseYamlFile,
   safeFileOperation,
 };