README: badges

Author: xushiwei

README.md

@@ -1,5 +1,10 @@
 # plan9asm
 
+[![Build Status](https://github.com/xgo-dev/plan9asm/actions/workflows/go.yml/badge.svg)](https://github.com/xgo-dev/plan9asm/actions/workflows/go.yml)
+[![GitHub release](https://img.shields.io/github/v/tag/xgo-dev/plan9asm.svg?label=release)](https://github.com/xgo-dev/plan9asm/releases)
+[![Coverage Status](https://codecov.io/gh/xgo-dev/plan9asm/branch/main/graph/badge.svg)](https://codecov.io/gh/xgo-dev/plan9asm)
+[![GoDoc](https://pkg.go.dev/badge/github.com/xgo-dev/plan9asm.svg)](https://pkg.go.dev/github.com/xgo-dev/plan9asm)
+
 `github.com/xgo-dev/plan9asm`
 
 Plan 9 assembly parser and LLVM IR translator, extracted as an independent module.