refactor: restructure for Claude Code plugin support

- Move skills into skills/ subdirectory per Claude Code plugin structure
- Add .claude-plugin/plugin.json for AEM Edge Delivery Services plugin
- Add root .claude-plugin/marketplace.json for plugin distribution
- Update README with Claude Code Plugins installation instructions

Plugin can now be installed via:
  /plugin marketplace add adobe/skills
  /plugin install aem-edge-delivery-services@adobe-skills

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: shsteimer

.claude-plugin/marketplace.json

@@ -0,0 +1,16 @@
+{
+  "name": "adobe-skills",
+  "owner": {
+    "name": "Adobe"
+  },
+  "metadata": {
+    "description": "Official Adobe skills for AI coding agents"
+  },
+  "plugins": [
+    {
+      "name": "aem-edge-delivery-services",
+      "source": "./skills/aem/edge-delivery-services",
+      "description": "Skills for AEM Edge Delivery Services development"
+    }
+  ]
+}

README.md

@@ -0,0 +1,11 @@
+{
+  "name": "aem-edge-delivery-services",
+  "description": "Skills for AEM Edge Delivery Services development, including Content Driven Development workflow, block building, testing, content modeling, code review, and page migration.",
+  "version": "1.0.0",
+  "author": {
+    "name": "Adobe"
+  },
+  "repository": "https://github.com/adobe/skills",
+  "license": "Apache-2.0",
+  "keywords": ["aem", "edge-delivery-services", "adobe", "blocks", "development"]
+}