README.md: Add automount key and map, fix ref to hbacsvcgroup and test

The main REAADME has been fixed to contain information about the
automount key and map modules, the reference to the hbacsvcgroup README
has been fixed and a new test has been added as a github workflow.

.github/workflows/readme.yml

@@ -0,0 +1,16 @@
+---
+name: readme test
+on:
+  - push
+  - pull_request
+jobs:
+  ansible_test:
+    name: Verify readme
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Run readme test
+        run: |
+          error=0
+          for i in README-*.md; do grep -q $i README.md && echo "OK: $i" || { echo -e "\033[31;1mERROR: ${i} missing\033[0m"; error=1; } done
+          exit $error