docs: change theme to furo (#4809)

Trying out a new theme -- I really like the way `furo` looks and I think
it makes it easier to navigate our overly dense docs pages.

docs/conf.py

@@ -156,29 +156,14 @@ modindex_common_prefix = ["xonsh."]
 # documentation.
 if not on_rtd:
 
-    html_theme = "cloud"
+    html_theme = "furo"
 
     html_theme_options = {
-        "max_width": "1250px",
-        "minimal_width": "700px",
-        "relbarbgcolor": "#000000",
-        "footerbgcolor": "#FFFFE7",
-        "sidebarwidth": "322px",
-        "sidebarbgcolor": "#e7e7ff",
-        #'googleanalytics_id': 'UA-41934829-1',
-        "inline_admonitions": True,
-        "stickysidebar": False,
-        "highlighttoc": False,
-        "externalrefs": False,
-        "collapsiblesidebar": True,
-        "default_layout_text_size": "100%",  # prevents division by zero error
-        "fontcssurl": "https://fonts.googleapis.com/css?family=Noticia+Text|Open+Sans|Droid+Sans+Mono",
+        "source_repository": "https://github.com/xonsh/xonsh/",
+        "source_branch": "main",
+        "source_directory": "docs/",
     }
 
-    # Add any paths that contain custom themes here, relative to this directory.
-    html_theme_path = ["_theme"]
-    templates_path = ["_templates_overwrite", "_templates"]
-
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
 # html_title = None
@@ -199,7 +184,6 @@ html_favicon = "_static/magic_conch.ico"
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ["_static"]
-html_style = "numpy_friendly.css"
 
 html_extra_path = ["_static/robots.txt"]
 

news/furo.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* New docs theme ``furo``
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

pyproject.toml

@@ -137,7 +137,7 @@ dev = [
 ]
 doc = [
     "xonsh[bestshell]",
-    "cloud_sptheme",
+    "furo",
     "numpydoc",
     "sphinx>=3.1",
     "psutil",