chore: configure miniconda for readthedocs builder

See error  readthedocs/readthedocs.org#9527 (comment)

Author: Francisco Aranda

.readthedocs.yaml

@@ -5,13 +5,19 @@
 # Required
 version: 2
 
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "miniconda3-4.7"
+
+
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
-   configuration: docs/conf.py
+  configuration: docs/conf.py
 
 # Optionally build your docs in additional formats such as PDF
 formats:
-   - pdf
+  - pdf
 
 conda:
-   environment: environment_docs.yml
+  environment: environment_docs.yml