ci: specify self-install in docs/requirements.txt

Author: jpgrayson

.readthedocs.yaml

@@ -11,10 +11,6 @@ build:
 python:
   install:
     - requirements: docs/requirements.txt
-    - method: pip
-      path: .
-      extra_requirements:
-        - .
 
 sphinx:
   configuration: docs/conf.py

docs/requirements.txt

@@ -1,2 +1,10 @@
+# This primarily exists for the readthedocs.io build, but may
+# also be useful for building docs in a local virtualenv:
+#
+#   python -m venv .venv
+#   source .venv/bin/activate
+#   pip install -r docs/requirements.txt
+#   make docs
+.
 setuptools_scm
 sphinx-rtd-theme