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>

hello-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,14 @@
+{
+  "name": "hello-plugin",
+  "description": "Plugin de exemplo para Claude Code. Demonstra skills, agents e hooks num formato minimo e didactico.",
+  "version": "1.0.0",
+  "author": {
+    "name": "Emanuel Almeida",
+    "url": "https://descomplicar.pt"
+  },
+  "homepage": "https://git.descomplicar.pt/ealmeida/hello-plugin",
+  "repository": "https://git.descomplicar.pt/ealmeida/hello-plugin.git",
+  "license": "MIT",
+  "keywords": ["example", "tutorial", "hello-world"],
+  "skills": "./"
+}