CI: migrate to GitHub Actions

Author: azu

.github/workflows/test.yml

@@ -0,0 +1,20 @@
+name: test
+on: [push, pull_request]
+jobs:
+  test:
+    name: "Test on Node.js ${{ matrix.node-version }}"
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [12, 14, 16]
+    steps:
+      - name: checkout
+        uses: actions/checkout@v2
+      - name: setup Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v2
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: Install
+        run: yarn install
+      - name: Test
+        run: yarn test

.travis.yml

@@ -1,4 +1,4 @@
-# @textlint/regexp-string-matcher [![Build Status](https://travis-ci.org/textlint/regexp-string-matcher.svg?branch=master)](https://travis-ci.org/textlint/regexp-string-matcher)
+# @textlint/regexp-string-matcher [![Actions Status: test](https://github.com/textlint/regexp-string-matcher/workflows/test/badge.svg)](https://github.com/textlint/regexp-string-matcher/actions?query=workflow%3A"test")
 
 Regexp-like string matcher library.