docs: adding Go version/release badges (aws#77)

Add Shield.io badges for Go version and GitHub release.
Useful for displaying important information in a visually appealing and easily accessible way at a glance.

Updated the license badge to standard Shield.io format.
As it appears it was incorrect pointing to the badge for 'aws-sam-local'.

Author: Callum Bodels

README.md

@@ -1,6 +1,8 @@
 ## AWS Lambda Runtime Interface Emulator
+![GitHub release (latest by date)](https://img.shields.io/github/v/release/aws/aws-lambda-runtime-interface-emulator)
+![GitHub go.mod Go version](https://img.shields.io/github/go-mod/go-version/aws/aws-lambda-runtime-interface-emulator)
+![GitHub](https://img.shields.io/github/license/aws/aws-lambda-runtime-interface-emulator)
 
-![Apache-2.0](https://img.shields.io/npm/l/aws-sam-local.svg)
 
 The Lambda Runtime Interface Emulator is a proxy for Lambda’s Runtime and Extensions APIs, which allows customers to
 locally test their Lambda function packaged as a container image. It is a lightweight web-server that converts