Add readthedocs configuration file (#2627)

* Add readthedocs configuration file

Co-authored-by: Manuel Schlund <manuel.schlund@dlr.de>
Co-authored-by: Klaus Zimmermann <klaus.zimmermann@smhi.se>

.readthedocs.yaml

@@ -0,0 +1,25 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.10"
+
+# Build documentation in the docs/sphinx/source directory with Sphinx
+sphinx:
+   configuration: doc/sphinx/source/conf.py
+
+# If using Sphinx, optionally build your docs in additional formats such as PDF
+formats:
+   - pdf
+
+# Optionally declare the Python requirements required to build your docs
+python:
+   install:
+   - requirements: doc/sphinx/source/requirements.txt

doc/sphinx/source/community/code_documentation.rst

@@ -332,7 +332,9 @@ CircleCI_ will build the documentation with the command
 to catch mistakes that can be detected automatically.
 
 The configuration file for Sphinx_ is
-`doc/shinx/source/conf.py <https://github.com/ESMValGroup/ESMValTool/blob/main/doc/sphinx/source/conf.py>`_.
+`doc/sphinx/source/conf.py <https://github.com/ESMValGroup/ESMValTool/blob/main/doc/sphinx/source/conf.py>`_
+and the configuration file for ReadTheDocs is
+`.readthedocs.yaml <https://github.com/ESMValGroup/ESMValTool/blob/main/.readthedocs.yaml>`_.
 
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