feat: marketplace inicial com hello-plugin

Marketplace Descomplicar para plugins Claude Code.
Primeiro plugin: hello-plugin (exemplo didactico com skill, agent, hook)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -0,0 +1,23 @@
+{
+  "name": "descomplicar-plugins",
+  "owner": {
+    "name": "Descomplicar",
+    "url": "https://descomplicar.pt"
+  },
+  "description": "Marketplace de plugins Claude Code da Descomplicar - ferramentas para agencia digital portuguesa",
+  "homepage": "https://git.descomplicar.pt/ealmeida/claude-plugins",
+  "repository": "https://git.descomplicar.pt/ealmeida/claude-plugins.git",
+  "plugins": [
+    {
+      "name": "hello-plugin",
+      "source": "./hello-plugin",
+      "description": "Plugin de exemplo que demonstra skills, agents e hooks",
+      "version": "1.0.0",
+      "author": {
+        "name": "Emanuel Almeida"
+      },
+      "keywords": ["example", "tutorial"],
+      "category": "tutorial"
+    }
+  ]
+}