Use GitHub workflows for CI

.github/workflows/test.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+set -o errexit
+set -o nounset
+
+if [ "$EMACS_VERSION" = '23.4' ]; then
+    curl -O 'https://github.com/raw/ohler/ert/c619b56c5bc6a866e33787489545b87d79973205/lisp/emacs-lisp/ert.el'
+fi
+
+EMACS="${EMACS:=emacs}"
+
+"$EMACS" -Q -batch --eval '(setq byte-compile-error-on-warn t)' -f batch-byte-compile rainbow-delimiters.el
+"$EMACS" -Q -batch -l rainbow-delimiters-test.el -f ert-run-tests-batch-and-exit

.github/workflows/test.yml

@@ -0,0 +1,27 @@
+name: CI
+
+on:
+  push:
+    paths-ignore:
+    - '**/*.md'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        emacs_version:
+          - 23.4
+          - 24.5
+          - 25.3
+          - 26.3
+          - snapshot
+    env:
+      EMACS_VERSION: ${{ matrix.emacs_version }}
+    steps:
+    - uses: purcell/setup-emacs@master
+      with:
+        version: ${{ matrix.emacs_version }}
+    - uses: actions/checkout@v1
+    - name: Run tests
+      run: './.github/workflows/test.sh'