docs: add Trivy security scan badge to README

- Add a Trivy Security Scan badge to the README for improved visibility of security status

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

Author: appleboy

README.md

@@ -1,5 +1,7 @@
 # Gin Examples
 
+[![Trivy Security Scan](https://github.com/gin-gonic/examples/actions/workflows/trivy-scan.yml/badge.svg)](https://github.com/gin-gonic/examples/actions/workflows/trivy-scan.yml)
+
 This repository contains a number of ready-to-run examples demonstrating various use cases of [Gin](https://github.com/gin-gonic/gin).
 
 Refer to the [Gin documentation](https://gin-gonic.com/en/docs/) for how to execute the example tutorials.