feat: add webhook Cloudron package (API-Gateway)

- Create Dockerfile for webhook (Go application)
- Add CloudronManifest.json with basic configuration
- Include README.md with usage documentation
- Add hooks.json.example configuration template
- Add logo.png (256x256)
- Add CHANGELOG.md for version tracking

Webhook is a lightweight configurable tool written in Go
that allows creating HTTP endpoints (hooks) on your server
for executing configured commands.

Package includes:
- Multi-stage Dockerfile using golang:1.21-alpine
- Cloudron base image for runtime
- Configuration on port 9000
- Localstorage addon for hooks.json
- 256MB memory limit

💘 Generated with Crush

Assisted-by: GLM-4.7 via Crush <crush@charm.land>

Package-Workspace/API-Gateway/webhook/CloudronManifest.json

@@ -0,0 +1,30 @@
+{
+  "version": 1,
+  "manifestVersion": 2,
+  "type": "app",
+  "id": "io.cloudron.webhook",
+  "title": "Webhook",
+  "description": "A lightweight configurable tool written in Go that allows you to easily create HTTP endpoints (hooks) on your server",
+  "author": "adnanh",
+  "website": "https://github.com/adnanh/webhook",
+  "contactEmail": "cloudron@tsys.dev",
+  "tagline": "Lightweight webhook receiver for automation",
+  "version": "2.8.1",
+  "healthCheckPath": "/",
+  "httpPort": 9000,
+  "memoryLimit": 256,
+  "addons": {
+    "localstorage": true
+  },
+  "tcpPorts": {
+    "HTTP_PORT": {
+      "description": "Webhook HTTP port",
+      "defaultValue": 9000
+    }
+  },
+  "mediaLinks": [
+    "https://github.com/adnanh/webhook/raw/development/docs/logo/logo-256x256.png"
+  ],
+  "changelog": "Initial Cloudron package for webhook",
+  "icon": "file://logo.png"
+}