Fix RTD builds

.gitignore

@@ -12,3 +12,4 @@ docs/source/_build
 man/ansi2html.1.xml
 src/ansi2html/_version.py
 site
+_readthedocs

.readthedocs.yml

@@ -0,0 +1,22 @@
+---
+version: 2
+
+mkdocs:
+  fail_on_warning: true
+  configuration: mkdocs.yml
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+  commands:
+    - pip install --user tox
+    - python3 -m tox -e docs
+python:
+  install:
+    - method: pip
+      path: tox
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs

tox.ini

@@ -71,4 +71,4 @@ commands =
     ;   --attribute="manual_version=$(python3 -m setuptools_scm)" \
     ;   --format=manpage -D man \
     ;   man/ansi2html.1.txt'
-    mkdocs build --strict
+    mkdocs {posargs:build --strict --site-dir=_readthedocs/html/}