ci: use gh-actions (#87)

Closes #86

> Owners may want to remove the Travis CI build

.github/workflows/ci.yml

@@ -0,0 +1,30 @@
+name: CI
+on: [push, pull_request]
+jobs:
+  test:
+    name: ${{ matrix.node-version }} ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macOS-latest, windows-latest, ubuntu-latest]
+        node-version: [10, 12, 14]
+    steps:
+      - uses: actions/checkout@v2
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: Install
+        run: npm i
+      - name: Tests
+        run: npm test
+
+  automerge:
+    needs: test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: fastify/github-action-merge-dependabot@v1
+        if: ${{ github.actor == 'dependabot[bot]' && github.event_name == 'pull_request' }}
+        with:
+          github-token: ${{secrets.github_token}}

README.md

@@ -1,4 +1,4 @@
-msgpack5  [![Build Status](https://travis-ci.org/mcollina/msgpack5.png)](https://travis-ci.org/mcollina/msgpack5)
+msgpack5  [![CI](https://github.com/mcollina/msgpack5/workflows/CI/badge.svg)](https://github.com/mcollina/msgpack5/actions?query=workflow%3ACI)
 ========
 
 A msgpack v5 implementation for node.js and the browser, with extension point support.