docs: add ReadTheDocs configuration

- Add .readthedocs.yaml for RTD build configuration
- Add docs/requirements.txt with minimal dependencies for docs build
- Configure Python 3.11 and Ubuntu 22.04 build environment
- Enable MkDocs documentation building on ReadTheDocs

Author: claude

.readthedocs.yaml

@@ -0,0 +1,28 @@
+# Read the Docs configuration file for hier-config-cli
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+version: 2
+
+# Build documentation in the "docs/" directory with MkDocs
+mkdocs:
+  configuration: mkdocs.yml
+  fail_on_warning: false
+
+# Set the version of Python
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+  jobs:
+    post_checkout:
+      # Generate any build-time dependencies or files here
+      - echo "Building hier-config-cli documentation"
+    post_install:
+      # Show installed packages for debugging
+      - pip list
+
+# Python dependencies required to build the docs
+python:
+  install:
+    # Install Poetry
+    - requirements: docs/requirements.txt

docs/requirements.txt

@@ -0,0 +1,3 @@
+# Documentation build requirements for ReadTheDocs
+mkdocs>=1.5.3
+mkdocs-material>=9.5.3