Add GHA test for this action

.github/file.rst

@@ -0,0 +1,12 @@
+Some errors
+===========
+
+Those triple backticks are not a thing in rst:
+```here```.
+
+Here ``Callable``s the "s" should be separated from ``Callable`` using
+a "backslash-space".
+
+... versionchanged:: 3.11
+    Raises :exc:`TypeError` instead of :exc:`AttributeError` if *cm*
+    is not a context manager.

.github/workflows/test.yml

@@ -0,0 +1,19 @@
+name: Test
+
+on:
+  push:
+    branches:
+      main
+  pull_request:
+    branches:
+      main
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: ./
+    - run: pip install sphinx-lint>=0.9.0
+    - run: sphinx-lint .github/file.rst >/dev/null
+      continue-on-error: true