Add testing workflow for github actions

.github/workflows/test.yml

@@ -0,0 +1,18 @@
+on: [push, pull_request]
+name: test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.16.x, 1.17.x]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Test
+        run: go test ./...

README.md

@@ -1,6 +1,6 @@
 <p align="center"><img src="logo/LOGOTYPE-HORIZONTAL-BLUE.png"></p>
 
-# Pixel [![Build Status](https://travis-ci.org/faiface/pixel.svg?branch=master)](https://travis-ci.org/faiface/pixel) [![GoDoc](https://godoc.org/github.com/faiface/pixel?status.svg)](https://godoc.org/github.com/faiface/pixel) [![Go Report Card](https://goreportcard.com/badge/github.com/faiface/pixel)](https://goreportcard.com/report/github.com/faiface/pixel) [![Join the chat at https://gitter.im/pixellib/Lobby](https://badges.gitter.im/pixellib/Lobby.svg)](https://gitter.im/pixellib/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Discord Chat](https://img.shields.io/discord/699679031603494954)](https://discord.gg/q2DK4MP)  
+# Pixel [![GoDoc](https://godoc.org/github.com/faiface/pixel?status.svg)](https://godoc.org/github.com/faiface/pixel) [![Go Report Card](https://goreportcard.com/badge/github.com/faiface/pixel)](https://goreportcard.com/report/github.com/faiface/pixel) [![Join the chat at https://gitter.im/pixellib/Lobby](https://badges.gitter.im/pixellib/Lobby.svg)](https://gitter.im/pixellib/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Discord Chat](https://img.shields.io/discord/699679031603494954)](https://discord.gg/q2DK4MP)  
 
 A hand-crafted 2D game library in Go. Take a look into the [features](#features) to see what it can
 do.