Add root-level Secret template and update .gitignore

Added Secret template for API7 Gateway credentials management
and improved .gitignore to prevent credential leaks.

Changes:

1. Secret Template (api7-credentials.yaml.template):
   - Template for creating API7 Gateway admin credentials Secret
   - Clear instructions for getting admin key from cluster
   - Examples for both stringData and base64 encoded data
   - Must be copied and filled in, then applied to cluster

2. .gitignore Updates:
   - Added api7-credentials.yaml to ignore actual secrets
   - Added wildcard *-credentials.yaml for any credential files
   - Excluded templates (!*-credentials.yaml.template)
   - Improved comments for clarity

3. README.md:
   - Comprehensive quick start guide
   - Features overview
   - Installation steps with Secret creation
   - Documentation links
   - Basic troubleshooting

Security:
- Prevents committing actual credentials
- Clear separation between templates and actual secrets
- Instructions for secure credential management

Users should:
1. Copy api7-credentials.yaml.template
2. Fill in actual credentials
3. Apply to cluster
4. Never commit filled secrets to git

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

api7-credentials.yaml.template

@@ -0,0 +1,55 @@
+# API7 Gateway Credentials Secret Template
+#
+# This is a template for creating the API7 Gateway admin credentials secret.
+# DO NOT commit this file with actual credentials filled in!
+#
+# Usage:
+#   1. Copy this template: cp api7-credentials.yaml.template api7-credentials.yaml
+#   2. Fill in the actual values (see instructions below)
+#   3. Apply to cluster: kubectl apply -f api7-credentials.yaml -n api7ee
+#   4. Update values.yaml to reference this secret:
+#      api7.gateway.existingSecret: "api7-credentials"
+#
+# IMPORTANT: Add api7-credentials.yaml to .gitignore!
+
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: api7-credentials
+  namespace: api7ee
+  labels:
+    app.kubernetes.io/name: api7ee-demo
+    app.kubernetes.io/component: api7-gateway
+type: Opaque
+stringData:
+  # Dashboard Admin API URL
+  # This is the HTTPS endpoint of the API7 Enterprise Dashboard
+  # Default: https://api7ee3-0-1759339083-dashboard:7443
+  admin-url: "https://api7ee3-0-1759339083-dashboard:7443"
+
+  # Admin API Key
+  # Get the actual key from the API7 Enterprise installation:
+  # kubectl get secret -n api7ee api7ee3-0-1759339083 -o jsonpath='{.data.admin_key}' | base64 -d
+  #
+  # REPLACE WITH YOUR ACTUAL KEY:
+  admin-key: "YOUR_ADMIN_KEY_HERE"
+
+  # Gateway Group
+  # Logical grouping of gateway instances
+  # Default: default
+  gateway-group: "default"
+
+---
+# Example using base64 encoded values (alternative to stringData)
+# apiVersion: v1
+# kind: Secret
+# metadata:
+#   name: api7-credentials
+#   namespace: api7ee
+# type: Opaque
+# data:
+#   # Base64 encoded values
+#   admin-url: aHR0cHM6Ly9hcGk3ZWUzLTAtMTc1OTMzOTA4My1kYXNoYm9hcmQ6NzQ0Mw==
+#   admin-key: WU9VUl9BRE1JTl9LRVlfSEVSRQ==
+#   gateway-group: ZGVmYXVsdA==