Add Read the Docs configuration file

.editorconfig

@@ -12,5 +12,8 @@ charset = utf-8
 [*.{xml,xsl,xsd,xd}]
 indent_size = 2
 
+[*.{yml,yaml}]
+indent_size = 2
+
 [*.{bat,cmd,ps1}]
 end_of_line = crlf

.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
+
+formats:
+  - epub
+  - pdf
+
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.8"
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  builder: html
+  configuration: docs/conf.py
+
+python:
+  install:
+    - requirements: docs/requirements.txt

docs/requirements.txt

@@ -1,2 +1,14 @@
-sphinx
+# By default, ReadTheDocs installs the following old versions:
+# https://github.com/readthedocs/readthedocs.org/issues/7858
+#
+# mock==1.0.1
+# pillow==5.4.1
+# alabaster>=0.7,<0.8,!=0.7.5
+# commonmark==0.8.1
+# recommonmark==0.5.0
+# sphinx<2
+# sphinx-rtd-theme<0.5
+# readthedocs-sphinx-ext<2.2
+
+Sphinx~=4.3.0
 -e .