add RTD configuration

.readthedocs.yaml

@@ -0,0 +1,22 @@
+version: 2
+
+build:
+  os: "ubuntu-22.04"
+  tools:
+    python: "3.12"
+  apt_packages:
+    - libdjvulibre-dev
+  jobs:
+    pre_build:
+      - python -m pip install Cython
+      - python setup.py build_ext --inplace
+
+sphinx:
+  configuration: doc/api/conf.py
+
+python:
+  install:
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs