fix: building sphinx rtd theme (#544)

* Add sphinx-rtd-theme to docs

First implementation

* docs: mobile friendly documentation

* docs: follow rtd installation instructions

.readthedocs.yaml

@@ -22,7 +22,10 @@ sphinx:
 # Optional but recommended, declare the Python requirements required
 # to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
+# Here we follow https://docs.readthedocs.io/en/stable/config-file/v2.html#packages
 python:
   install:
-    - sphinx
-    - sphinx-rtd-theme
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs