DOC: remove superscript formatting for citation callouts (pvlib#855)

* remove superscript formatting for footnotes via css override

* update conf.py comments

Author: kandersolar

docs/sphinx/source/_static/no_reference_superscript.css

@@ -0,0 +1,4 @@
+.footnote-reference {
+    font-size: 100% !important;  /* default is 90% */
+    top: 0.0em !important;  /* default is -0.4em */
+}

docs/sphinx/source/conf.py

@@ -223,9 +223,13 @@ def __getattr__(cls, name):
 # Output file base name for HTML help builder.
 htmlhelp_basename = 'PVLIB_Pythondoc'
 
-# A workaround for the responsive tables always having annoying scrollbars.
+
+# custom CSS workarounds
 def setup(app):
+    # A workaround for the responsive tables always having annoying scrollbars.
     app.add_stylesheet("no_scrollbars.css")
+    # Override footnote callout CSS to be normal text instead of superscript
+    app.add_stylesheet("no_reference_superscript.css")
 
 
 # -- Options for LaTeX output ---------------------------------------------