Replace TravisCI with GitHub Actions (#13)

Author: duffn

.github/workflows/test.yml

@@ -0,0 +1,32 @@
+name: Tests
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Setup Firefox
+        uses: browser-actions/setup-firefox@latest
+        with:
+          firefox-version: "54.0"
+      - name: Download geckodriver
+        uses: browser-actions/setup-geckodriver@latest
+        with:
+          geckodriver-version: "0.18.0"
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: "2.6.6"
+          bundler-cache: true
+      - name: Start MongoDB
+        uses: supercharge/[email protected]
+        with:
+          mongodb-version: "5"
+          mongodb-db: slack-ruby-bot-server-stripe_sample_test
+      - name: Run tests
+        uses: GabrielBB/xvfb-action@v1
+        with:
+          run: bundle exec rake

.travis.yml

@@ -1,7 +1,7 @@
 Slack Ruby Bot Server Stripe Sample
 ===================================
 
-[![Build Status](https://travis-ci.org/slack-ruby/slack-ruby-bot-server-stripe-sample.svg?branch=master)](https://travis-ci.org/slack-ruby/slack-ruby-bot-server-stripe-sample)
+[![test](https://github.com/slack-ruby/slack-ruby-bot-server-stripe-example/actions/workflows/test.yml/badge.svg)](https://github.com/slack-ruby/slack-ruby-bot-server-stripe-example/actions/workflows/test.yml)
 
 ### What is this?