Echo Version 4.9.0 no longer compatible with go 1.14+

[TristanSpeakEasy]

Issue Description

Echo Version 4.9.0 no longer compatible with go 1.14+

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

echo works with go version 1.14+ as detailed in the Readme https://github.com/labstack/echo/blob/master/README.md#supported-go-versions

Actual behaviour

Version 4.9.0 of Echo now introduces as dependency on the io/fs packages that causes applications build on go versions below 1.16 to fail compilation

Steps to reproduce

Include echo version 4.9.0 in a go lang application built on 1.14 or 1.15 of go

Working code to debug

package main

func main() {
}

Version/commit

4.9.0

[aldas]

Readme is updated by #2291