CI: Create script for running GitHub workflow locally

.github/workflows/test.yml

@@ -7,9 +7,5 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v1
-      - name: Build
-        run: docker build . --file Dockerfile -t stumpwm
-      - name: Test
-        run: docker run stumpwm make test
-      - name: Integration_Testing
-        run: cd tests/integration-tests; ./script ci
+      - name: Run CI script
+        run: ./ci

README.md

@@ -140,6 +140,8 @@ that your contribution gets merged in a timely manner:
     informed on stumpwm-devel! Also, it will probably help if the
     changes are made and then incrementally applied to the codebase in
     order to avoid introducing show-stopping bugs.
+  * Run `./ci` before making a pull request to confirm that the GitHub
+    workflow will succeed.
 * Do not's
   * Include Emacs local variables
   * Change whitespace 

ci

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -e
+docker build . --file Dockerfile -t stumpwm
+docker run stumpwm make test
+cd tests/integration-tests
+./script ci