docs(README): add build status badge

Author: Fonger

.github/workflows/test.yml .github/workflows/build.yml.github/workflows/test.yml renamed to .github/workflows/build.yml

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-name: Node.js CI
+name: Build
 
 on:
   push:

README.md

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 # ts-transformer-optimize-const-enum
 
+![CI Status](https://github.com/Fonger/ts-transformer-optimize-const-enum/actions/workflows/build.yml/badge.svg)
+
 A typescript transpiler that transform exported const enum into object literal.
 
 This is just like the one from [@babel/preset-typescript with optimizeConstEnums: true](https://babeljs.io/docs/en/babel-preset-typescript#optimizeconstenums) but it works for typescript compiler.