docs: improve README formatting and section headers

This improves links rendering on pkg.go.dev.

README.md

@@ -1,12 +1,14 @@
-# fasthttp [![GoDoc](https://pkg.go.dev/badge/github.com/valyala/fasthttp)](https://pkg.go.dev/github.com/valyala/fasthttp) [![Go Report](https://goreportcard.com/badge/github.com/valyala/fasthttp)](https://goreportcard.com/report/github.com/valyala/fasthttp)
+# fasthttp
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/valyala/fasthttp)](https://pkg.go.dev/github.com/valyala/fasthttp) [![Go Report](https://goreportcard.com/badge/github.com/valyala/fasthttp)](https://goreportcard.com/report/github.com/valyala/fasthttp)
 
 ![FastHTTP – Fastest and reliable HTTP implementation in Go](https://github.com/fasthttp/docs-assets/raw/master/banner@0.5.png)
 
 Fast HTTP implementation for Go.
 
-# fasthttp might not be for you!
-fasthttp was designed for some high performance edge cases. **Unless** your server/client needs to handle **thousands of small to medium requests per second** and needs a consistent low millisecond response time fasthttp might not be for you. **For most cases `net/http` is much better** as it's easier to use and can handle more cases. For most cases you won't even notice the performance difference.
+## fasthttp might not be for you!
 
+fasthttp was designed for some high performance edge cases. **Unless** your server/client needs to handle **thousands of small to medium requests per second** and needs a consistent low millisecond response time fasthttp might not be for you. **For most cases `net/http` is much better** as it's easier to use and can handle more cases. For most cases you won't even notice the performance difference.
 
 ## General info and links