use github workflow instead of travis build

.github/workflows/build.yml

@@ -0,0 +1,13 @@
+name: Build
+on: [push, pull_request]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: apt
+      run: sudo apt-get install -y luarocks
+    - name: luacheck install
+      run: luarocks install --local luacheck
+    - name: luacheck run
+      run: $HOME/.luarocks/bin/luacheck ./

.travis.yml

@@ -1,11 +0,0 @@
-language: generic
-addons:
-  apt:
-    packages:
-    - luarocks
-before_install:
-  - luarocks install --local luacheck
-script:
-- $HOME/.luarocks/bin/luacheck ./
-notifications:
-  email: false

README.md

@@ -1,6 +1,6 @@
 # Powerbanks [powerbanks]
 
-[![Build Status](https://travis-ci.org/OgelGames/powerbanks.svg?branch=master)](https://travis-ci.org/OgelGames/powerbanks)
+[![Build](https://github.com/OgelGames/powerbanks/workflows/Build/badge.svg)](https://github.com/OgelGames/powerbanks/actions)
 [![License](https://img.shields.io/badge/License-MIT%20and%20CC%20BY--SA%204.0-green.svg)](LICENSE.md)
 [![Feedback](https://img.shields.io/badge/Feedback-Minetest%20Forum-lightgrey.svg)](https://forum.minetest.net/viewtopic.php?t=23791)
 [![Download](https://img.shields.io/badge/Download-ContentDB-blue.svg)](https://content.minetest.net/packages/OgelGames/powerbanks)