docs(readme): update ci badge syntax (#1263)

* docs(readme): update ci badge syntax

* Update README.md

Signed-off-by: Frazer Smith <frazer.dev@icloud.com>

---------

Signed-off-by: Frazer Smith <frazer.dev@icloud.com>

README.md

@@ -1,6 +1,6 @@
 # @fastify/passport
 
-[![CI](https://github.com/fastify/fastify-passport/workflows/CI/badge.svg)](https://github.com/fastify/fastify-passport/actions/workflows/ci.yml)
+[![CI](https://github.com/fastify/fastify-passport/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/fastify/fastify-passport/actions/workflows/ci.yml)
 [![NPM version](https://img.shields.io/npm/v/@fastify/passport.svg?style=flat)](https://www.npmjs.com/package/@fastify/passport)
 [![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg?style=flat)](https://github.com/prettier/prettier)