switch to furo, a simpler theme

the theme allows us to use more top level sections

Author: rmorshea

docs/main.py

@@ -20,7 +20,7 @@
 
 @app.route("/")
 async def forward_to_index(request):
-    return response.redirect("/docs/content/index.html")
+    return response.redirect("/docs/index.html")
 
 
 mount, element = multiview()

docs/source/exts/async_doctest.py renamed to docs/source/_exts/async_doctest.py

@@ -1,4 +1,3 @@
-import textwrap
 from pathlib import Path
 
 from sphinx.application import Sphinx
@@ -112,7 +111,7 @@ def _literal_include_js_lines(name, linenos):
 
 
 def _string_to_nested_lines(content):
-    return StringList(textwrap.indent(content, "    ").split("\n"))
+    return StringList(content.split("\n"))
 
 
 def setup(app: Sphinx) -> None: