refactor: revise plugin metadata format and clean up redundant fields

- Replace plugin.json with marketplace.json to update the plugin metadata structure
- Remove redundant fields such as keywords, homepage, repository, license, and author email
- Group author and metadata sections for improved clarity and organization

Signed-off-by: appleboy <[email protected]>

Author: appleboy

.claude-plugin/marketplace.json

@@ -0,0 +1,22 @@
+{
+  "name": "CodeGPT",
+  "owner": {
+    "name": "Bo-Yi Wu",
+    "url": "https://github.com/appleboy"
+  },
+  "metadata": {
+    "description": "A CLI tool for generating git commit messages and code reviews using AI. Supports multiple providers including OpenAI, Azure, Gemini, Anthropic, Ollama, Groq, and OpenRouter.",
+    "version": "1.0.0"
+  },
+  "plugins": [
+    {
+      "name": "generating-commit-messages",
+      "description": "This skill provides AI-powered git commit message generation using the `codegpt commit` command. It analyzes git diffs and automatically generates conventional commit messages in multiple languages.",
+      "source": "./",
+      "strict": false,
+      "skills": [
+        "./skills/commit-helper"
+      ]
+    }
+  ]
+}