use dynamic build process for RTD

.readthedocs.yml

@@ -5,6 +5,9 @@ build:
   os: "ubuntu-22.04"
   tools:
     python: "3.11"
+  commands:
+    - pip install --no-cache-dir -r docs/requirements-docs.txt
+    - python -m mkdocs build --clean --site-dir $READTHEDOCS_OUTPUT/html --config-file mkdocs.yml
 
 python:
   install:

mkdocs.yml

@@ -1,5 +1,5 @@
 site_name: Freqtrade
-site_url: https://www.freqtrade.io/en/latest/
+site_url: !ENV [READTHEDOCS_CANONICAL_URL, 'https://www.freqtrade.io/en/latest/']
 repo_url: https://github.com/freqtrade/freqtrade
 edit_uri: edit/develop/docs/
 use_directory_urls: True