Update .readthedocs.yaml

Author: pockerman

.readthedocs.yaml

@@ -15,6 +15,9 @@ build:
     install:
       - doxygen
       - pip install sphinx
+      - pip install breathe
+      - pip install exhale
+      - pip install sphinx_rtd_theme
 
 
 # Build documentation in the "docs/" directory with Sphinx