This is the initial restructure of docs with Antora

While it's hardly complete, it's enough to get started. This change
presents the first, most basic Antora implementation of the
documentation, along with the beginnings of the restructure and
rewriting of the documentation.

Author: settermjd

docs-site/antora-playbook.yml

@@ -0,0 +1,12 @@
+site:
+  title: The laminas-db documentation
+  start_page: laminas-db-documentation::index.adoc
+content:
+  sources:
+  - url: ../
+    branches: HEAD
+    start_path: docs-site
+ui:
+  bundle:
+    url: https://gitlab.com/antora/antora-ui-default/-/jobs/artifacts/HEAD/raw/build/ui-bundle.zip?job=bundle-stable
+    snapshot: true

docs-site/antora.yml

@@ -0,0 +1,5 @@
+name: laminas-db-documentation
+version: ~
+title: The laminas-db documentation
+nav:
+  - modules/ROOT/nav.adoc