Add a workflow for checking asciidoc in README

Author: jmid

.github/workflows/check-asciidoc.yml

@@ -0,0 +1,17 @@
+name: build
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+jobs:
+  run:
+    name: Check asciidoc
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - run: sudo apt install asciidoc-base
+    - run: asciidoc README.adoc
+